The only issue with modern modding is that they become obsolete with pretty much every update and modders burn out (former modder myself) and we canâ€™t keep up. We move on, but some ppl still use our mods. Update and boom no more mod. I have games that I canâ€™t even imagine playing unmoderated (looking at you Skyrim).
iirc modding the party size is trivial, merely a tweak of a text file (which shows that it is a deliberate choice by Larian).