"factoring" subordinate clauses with verbs that require indicative and subjunctive clauses

The difficulty arises from the different constructions that can follow the two verbs demand and expect. You can demand that someone do something, but you can’t expect that someone do something. It follows that it is not grammatically coherent to say either ‘You cannot demand nor expect that he read the appendices’ or ‘You cannot demand nor expect that he reads the appendices’ or ‘You cannot demand nor expect that he will read the appendices’ is.

Not only can you avoid that sort of construction, as you suggest, but you must, if you want to make life easy for the reader. A possible alternative is ‘You cannot demand that he read the appendices, and you cannot expect him to either.’

Fortunately, English has an auxiliary verb that goes with both demand and expect:

You cannot demand or expect that he should read the appendices.

But this doesn't answer the question for general pairs of verbs.

I know of no absolute rule, and so would depend upon the proximity principle to produce something that hopefully read well:

You cannot demand nor expect that he will read the appendices.

You cannot expect nor demand that he read the appendices.

The proximity principle is more an observation than a rule - in cases where there is a conflict of agreement because of two or more words being joined by a conjunction that would require a different number, mood, etc. in what follows, then make the agreement happen with those words that are closer to each other and it will tend to sound correct whether it is or not!

However, if what was added could be read as a parenthetical clause, then I would treat it as if it could be omitted:

You cannot demand, nor expect, that he read the appendices.

You cannot expect, nor demand, that he will read the appendices.

Again though, I know of no absolute rule.

In general, when we factor out into a list, we make the common factor agree with the closest member of the list. For example:

There was a cat and two dogs.

There were two dogs and a cat.

You can neither demand, nor expect that he will read the appendices.

You can neither expect, nor demand that he read the appendices.