What kind of construct is 'would that that were all'?

I would here is an archaic way of saying I wish.

See the other answers for a fuller picture

The author clearly does not want to repeat the I wish

I wish I were ....., but I also wish that that were all!

I read

I may just be affected by the strangeness of this night, but wish that that was the only reason I feel uneasy

This is the kinda of would which is the past tense of the non-modal version of will. The OED calls this use either obsolete or rare archaic — and it is of course the latter of those that here obtains.

Dracula’s “would that that were all” is actually an optative that means the same thing as “O that that were all!” or “if only that were all!”. In other words, he wishes that it were so. As an optative, one traditionally employs the past subjunctive in the other clause, as the OED (eventually) explains below .

First off, if you look at the OED entry for will, you find that when used with a simple object, would means

22. Desired, wished for; sometimes implying or passing into the sense ‘intended’;

And when used with (amongst other things) an infinitive complement, it means:

23. Desired, wished; often implying ‘intended’; determined, ordained; fig. demanded, required (that something should be done)

Citations of the latter include:

• 1513 Douglas Æneis viii. vi. 26 - He..wald also this regioun euery steid War callit Latium.
• 1535 Coverdale 1 Macc. iv. 27 - Because Israel had not gotten soch mysfortune as he wolde they shulde.
• 1542 Udall Erasm. Apoph. 327 - He would his richesse to bee a cloke of goodnesse.
• 1600 Shaks. A.Y.L. iii. ii. 161 - Heauen would that shee these gifts should haue.
• 1682 Bunyan Holy War (1905) 263 - He would that Captain Credence should join himself with them.
• 1868 Tennyson Lucretius 68 - Because I would not one of thine own doves, Not ev’n a rose, were offer’d to thee.

This is quite close to:

36. Similarly with const. as in 2: viz. with obj. clause, with vb. in past subj. (arch. except in would rather or sooner = ‘should prefer’), †rarely in pres. subj., or with acc. and inf. Hence (arch.) with ellipsis of 1st pers. pron. as an expression of longing = ‘I wish’, ‘O that’; also, by confusion with 37, in the form (I) would to God (or heaven).

Which includes in its citations:

• 1816 J. Wilson City of Plague ii. i, - At a sad hour the sailor hath return’d; Would he were yet at sea!
• 1831 Scott Ct. Rob. xix, - I would to God I had more.
• 1865 Whittier Kallundborg Church 48 - Would I might die now in thy stead!
• 1882 Tennyson Charge of the Heavy Brigade Epil. 10-11, - I would that wars should cease, I would the globe from end to end Might sow and reap in peace.

This is in fact an optative use, as spelt out in sense 37:

37. Used optatively in the phr. would God (also God would, Christ would) = ‘O that God would’, ‘O that it were God’s will’, as an expression of earnest desire or longing. Obs. or rare arch.

There are many other uses of would that the OED explains at length under its entry for will, that are related to this and which are in no way strictly temporaal, often taking past subjective or which have past into a “conditional mood”.

Will (and therefore would) is an extremely exceedingly complex verb in English, perhaps the hardest to master. This is particularly true if you take into account uses that, although strictly speaking are indeed part of Modern English, are now perceived as literary, archaic, or poetic. Indeed, the OED has 68 citations for Shakespeare alone under its entry for will/would. Here are just a few of those for would:

• 1588 Shaks. L.L.L. v. ii. 174 - What would these strangers?
• 1588 Shaks. Tit. A. iii. i. 209 - What would thou kneele with me?
• 1590 Shaks. Mids. N. i. i. 195 - O that your frownes would teach my smiles such skil.
• 1590 Shaks. Mids. N. v. i. 255, - I am wearie of this Moone; would he would change.
• 1591 Shaks. Two Gent. iii. i. 110, - I would resort to her by night.
• 1591 Shaks. Two Gent. iii. i. 80 - What would your Grace haue me to do in this?
• 1591 Shaks. Two Gent. iv. iii. 22, - I would to Valentine To Mantua, where I heare, he makes aboad.
• 1592 Shaks. Rom. & Jul. ii. ii. 44 (Qo. 1) - That which we call a Rose, By any other name would smell as sweet.
• 1593 Shaks. 3 Hen. VI, ii. i. 75 - Now my Soules Pallace is become a Prison: Ah, would she breake from hence.
• 1595 Shaks. John iii. iv. 48, - I am not mad, I would to heauen I were.
• 1596 Shaks. Merch. V. i. iii. 66 - Is he yet possest How much ye would? Shy. I, I, three thousand ducats.
• 1596 Shaks. Tam. Shr. i. ii. 215 - Hor. I promist we would..beare his charge of wooing... Gremio. And so we wil.
• 1598 Shaks. Merry W. ii. i. 10 - You loue sacke, and so do I: would you desire better simpathie?
• 1598 Shaks. Merry W. ii. i. 189 - If hee should intend this voyage toward my wife, I would turne her loose to him.
• 1599 Shaks. Much Ado ii. iii. 119, - I would haue thought her spirit had beene inuincible against all assaults of affection.
• 1599 Shaks. Much Ado ii. iii. 6, - I know that, but I would haue thee hence, and heere againe.
• 1600 Shaks. A.Y.L. iii. ii. 161 - Heauen would that shee these gifts should haue.
• 1602 Shaks. Ham. iii. iii. 75 - That would be scann'd.
• 1603 Shaks. Meas. for M. iv. ii. 18, - I would bee glad to receiue some instruction.
• 1605 Shaks. Macb. i. vii. 44 - Letting I dare not, wait vpon I would.
• 1610 Shaks. Temp. ii. i. 185 - You would lift the Moone out of her spheare, if she would continue in it fiue weekes without changing. Seb. We would so, and then go a Bat-fowling.
• 1610 Shaks. Temp. iii. i. 61 - Fer. I am, in my condition A Prince (Miranda) I do thinke a King (I would not so).
• 1610 Shaks. Temp. iii. i. 61, - I..would no more endure This wodden slauerie, then to suffer The flesh-flie blow my mouth.
• 1611 Shaks. Cymb. ii. iv. 6 - Quake in the present winters state, and wish That warmer dayes would come.

See what I mean?

I have a strange feeling that not many gurus would agree with me on my analysis. But, WTH.

I don't think we should think of this pattern of expression as archaic. Rather, it is rare due to the rarity of occasions where we see the need for its subtlety.

I am proposing to look at the subjunctivity of the pattern.

Let us analyse the following illustrations.

A US marine , intelligence/recon team had been flown to Afghanistan, whose mission was to scout out evidence for the presence of AQAP in Afghanistan, which would mean the dire existence of cooperation between AQAP and the Taliban.

This morning, we are speaking to the Pashtun tribesmen. They tell us that they saw a man by the name Abu Rahmat-el-maut (agent of the mercy of death) whom we know was a courier of the New Mexican Awlaki. He distributed weapons and one of which is in our hands, which clearly had been part of Gaddafi's ransacked arsenal.

I wish that were not true. I wish we never found evidence of AQAP in Afghanistan. But, that is the evidence we need to show Congress and the govt of Pakistan.

If I were the soldier writing the report, to accurately reflect my conflicting sentiments, I would write

I would that were not true. I would that we had not found an item ransacked from Gaddafi's arsenal. Because, I would want to believe the Taliban were not in cooperation with AQAP. But I cannot wish for that, because that is what we came to retrieve, and because that is what we need to present to ...

And, another situation where police are pursuing evidence of a serial killer.

I would that we had not found the little girl's remains buried in his backyard. I really wish Amanda were alive and well, skipping about on her lawn and that no serial killer came to take her. OTOH, this is evidence that our team have been wishing for.

I wish (rather than I would) that people not shy away from this pattern of usage when the situation of conflict raises the opportunity for its use. Because, it beautifully and precisely expresses the conflict at hand.

Pls bear with me further, to remind what subjunctive is about. The subjunctive casts the speaker's present into the past. In subjunctive, we have roughly three patterns.

• impossibility: If I were a bird, I would sing all day. It is impossible for me to be a bird.
• optatative: Could you help me? I realise the improbability that you see the need to help me, but I politely reduce myself to asking the improbable (because if I asked "Can you help me?" would be presumptuously demanding and less polite).
• retrospective: I wish I were there when she passed away. I would have told her that I had forgiven her.