Your team member is at the state of the art. Sorry. He is right that it is something to be done at the very end of the project because any change to the TOC will require re-doing everything.

I'm curious as to why you are using chapter numbering, i.e. A-1, B-5, etc. This is normally only used when one is restarting numbering in each logical section. That, in itself, is a bad idea but is used widely.

Also, be aware of the SECTIONPAGES field.

Here are my references on Tables of Contents:
How to create a table of contents in Microsoft Word by Shauna Kelly
Generating a Table of Contents - Complex Documents

They do not provide a solution to your problem and you have probably already seen them. I list them in case they may help with other problems.

If I were submitting a bid, I think I would give two bids, one with, and the other without this strange feature.