>>7073787>>7073779to add onto what others said, my experience looking at past tabletop homebrews is that the most fleshed out ones that actually are designed like a skirmish/wargame rather then a TTRPG do not use Gunpla. In fact there is a line of 1/400 Gashapon that Bandai actually made official tabletop rules for. It is somewhat obscure information, don't think it was very well recieved in Japan but apparantly some people in the west liked it or at least the idea enough to get the rules translated.
Google 'gundam collection 1/400 tactical battle' for more info.
Of course considering the age of that mnis line, good luck finding them. might be able to use other lines though.