Is there no alternative to: "si simplement que tu te demanderas d’abord : n’aurait-il pas compris"?

Question

I believe this question arose from a misunderstanding of the text I quote. I only leave it because it has been answered and the mistake was instructive to myself. I doubt however reading this will be worthwhile to others.

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This question is on the highlighted sentence in this passage from chapter 7 of La porte étroite by André Gide.

     – Écoute, Alissa, m’écriai-je tout d’un coup : j’ai douze jours libres devant moi. Je n’en resterai pas un de plus qu’il ne te plaira. Convenons d’un signe qui voudra dire : c’est demain qu’il faut quitter Fongueusemare. Le lendemain, sans récriminations, sans plaintes, je partirai. Consens-tu ?
      N’ayant point préparé mes phrases, je parlais plus aisément. Elle réfléchit un moment, puis :
      – Le soir où, descendant pour dîner, je ne porterai pas à mon cou la croix d’améthyste que tu aimes… comprendras-tu ?
      – Que ce sera mon dernier soir.
      – Mais sauras-tu partir, reprit-elle, sans larmes, sans soupirs…
      – Sans adieux. Je te quitterai ce dernier soir comme je l’aurais fait la veille, si simplement que tu te demanderas d’abord : n’aurait-il pas compris ? mais quand tu me chercheras, le lendemain matin, simplement je ne serai plus là.
      – Le lendemain je ne te chercherai plus.

QUESTION

Am I right in thinking that demanderas and n’aurait-il pas compris as stand above are the only way to express the thought there being expressed and that there is neither a more formal nor more colloquial alternative to it?

If there is an alternative in either direction, please tell me what it is.

BACKGROUND

So often do I hear that what I find in some book is "literary" and would in conversation become something else--so often that I am constantly on the look out for such a possibility.

For the clause in question above, I seem to have determined that it is the only way anyone could have put it, whether in literature or conversation, as follows.

If we were at the actual moment of Alissa's wondering, the clause would run:

si simplement que tu te demandes d'abord : n'ait-iln'a-t-il pas compris ?

But we are not there yet. The moment still lies in the future; so everything has to go into a future tense. So, as the book has it:

si simplement que tu te demanderas d’abord : n’aurait-il pas compris ?

Answer 1

It looks to me like this is a happy medium between more formal and more colloquial (although there are probably ways to say that in slang, but I'm not sure your question is about that). I wouldn't venture in "n'eusse-t'il pas compris" territory - maybe there is a subjunctive possibility (!) but I don't want to go there. One could say:

si simplement que tu te demanderas d’abord: n’a-t-il pas compris?

In which there is less uncertainty.

One thing though:

si simplement que tu te demandes d'abord : n'ait-il pas compris ?

Doesn't work. It would have to be, maybe (but the agreement of the tenses feels wrong):

si simplement que tu te demandes d'abord : n'avait-il pas compris ?