Double quotes for plurals of words, letters and phrases [closed]

Are these within the realm of possibility -- that is, forming the plurals of letters, words, phrases, and numbers as I've done below?

No suggestions for italicizing, please.

"is"s, "as"s, "was"s, "maybe"s, "whereas"s, "thank-you"s

"A"s, "h"s

They said their "I do"s in a church in London.

All of the following are found in use:

1. Italics (I'm not suggesting it, I'm mentioning it as a case that is found in use, and I'm aiming at completeness): I dos; whereass or whereases.
2. Underlined, though only used when italics aren't available (e.g. with typewriters) to represent that italics should be used. (Can't give example in markdown, because markdown can do italics and so has no need for underline in most text).
3. With an apostrophe: I do’s; whereas's
4. With double-quotes: “I do”s; “whereas”s
5. With single-quotes: ‘I do’s; ‘whereas’s
6. Plain: I dos; whereases

None of these are incorrect, though some people do interpret the apostrophe-use as an example of “grocers’ apostrophe’s” where people use an apostrophe with a normal plural and which is generally considered incorrect. On the other hand, Edwin recommends in a comment above that you follow Lynne Truss's suggestions, and if I recall correctly, she favours apostrophe-s on plurals of mentions.

As a rule -s is used rather than -es with the forms that have something separating the -s from the rest of the word of phrase, -es is used where necessary on the plain form, and both approaches are found with italics.

I've listed them according to my personal preferences, though I'm actually about tied between double and single quotes, so I'd personally use whichever was the first one that I could use (e.g. depending on whether italics where available or not) and was allowed to use (if writing to a style guide that had rules on the matter). I'd argue in favour of that personal preference on the basis of clarity as to what is meant, but putting apostrophe use above quoting because it's a long-standing use.

I would though favour quoting over apostrophe if it was an actual repeat of what someone had said, rather than another type of mention, so I'd use quoting with “I do”s in your example since it's something actually said, but apostrophes with whereas’s .

But as a personal preference I'm not going to claim someone ordering these differently is wrong.