Can the notes area (at the bottom of the page) to be at the same height on facing pages? On all pages?

Question

The basic idea for our diglot layout is seen below. In our project, the secondary text of the diglot is an interlinear text on the inside part of facing pages (ideally with a decorative border). The primary text of the diglot is a vernacular translation, presented as a commentary of the interlinearized text, which includes extensive footnotes in the bottom notes area. 

The goal is for the height of the notes area to be the same so that it doesn't look wildly askew on facing pages. I'm not sure what the best solution to this is - have a fixed height for the notes area? Have a fixed height for the texts above? 

Similar products we have seen utilize a fixed-size border around the interlinearized text - This border is the same size size on every page and the rest of the material flows to match its verse numbers, etc. 

Is it a better approach to try to make the interlinear text (the secondary text of the diglot) the same size on every page? Or is it better to try to make the height of the notes area the same on every page? Or just on facing pages. Are any of these approaches possible?

Answer 1

If I can summarise your request:
1a. fixed sized notebox or
1b. grow the notebox for page N after processing page N+1
2. box around one translation.
3. A 'diglot' but not one which is aligned at paragraphs, instead flowing 'normally'.
4. All notes in one, full-width area (from both translations)

(4) is possible, I can't remember where it is in the user interface, but the switch is \diglotSepNotesfalse
The answer for 1-3  is somewhere between we can't do that and we can't do that yet.
(2) is a strong desire, but it demands a rewrite of multiple bits of code. Some of those changes are likely also needed for a new  (currently-in-development) polyglot-complexpages plugin I'm slowly chipping away at.

(1b) isn't possible with any of the current code. It might be possible for polyglot-complexpages. Given the amount of re-juggling you're implicitly asking for it will be slow  and there will be horribly messy situations with no easy answers: Imagine page X and X+1 are facing each other, but X+1 has a long note on it's last line. We grow page X's notespace so that it matches X+1, but that moves a line of text onto X+1, which in turn forces the long note at the end of X+1 onto the page X+2, so that now page X and X+1 have needless blank space and readers look at it and say "That's horrible, why did they do that?" I'm tempted to say it might be theoretically possible but I'm not going to go there.
IF, HOWEVER you tell me I can build a single block of notes from the combined notes from pages X and X+1, and then split it exactly in half, ignoring where the notes actually appear, then it's much easier, but someone probably gets lynched by the world's typesetters.

(1a) is confusing to me. Are you thinking you can guarantee that there will never be more that N lines of footnotes? How should the code react if you're wrong? TeX Does have something similar that would force a pagebreak within / before the footnote if the note takes too much of the page, but I expect it will only work with a very specific set of settings. (non-paragraphed notes being an absolute must at the moment, and probably no separate cross-references).
Adding additional space to the note area isn't possible yet, but would be a fairly trivial change to make.

(3) Is something that is probably going to be possible with the above-mentioned polyglot-complexpages plugin.