Quick update, I settled on 24 being the magic number, 4 being considered as backups. I managed to get 24 brand new IBM NETVISTA 6648 motherboards, which are 815 chipset boards, so no more VIA as an option. I also have another 7, Intel 815 boards which I will probably use to build systems to sell, to recover some of the investment. I got 31 3Coms 905Bs, that I managed to get to work after assigning exclusive IRQs on their PCI slots; I got 31 Sound Blaster Live's CT4780 and managed to get them to work. Kudos to "boxpressed", that uploaded here the only working drivers on the web (https://archive.org/details/sblive-1024). I got 10 PIII 1000 SL4C8s and will get the rest pretty soon; I got 31 brand new coolers; Settled on Wise keyboards and got 10 - they feel and sound perfect; As mice I went with the Perixx 10442 PS2 with 1000 DPI and got 10. I want to start designing the enclosures/cases, which will be see through and mounted on the desk above the monitors.

Not sure if any games of the time supported that many people. Quake 3 and Unreal for example had a max of 16 players and the majority only had 8.
Just something to keep in mind as of course nothing stopping you having multiple games going at once.

Will be interesting to see the cases, didn't realise you weren't just using some generic case. Gives you the opportunity to design something that's easy to service.

I honestly wish you luck with all this!