Increasing the maximum player models shown in the menu requires code changes.
The map limit in the skirmish menu was increased from ~90 to ~300. This is only increased if you use the ioq3 UI. It requires an ioq3 test build and setting vm_ui cvar to 0 on Windows and macOS to load baseq3\uix86_64.dll or baseq3/uix86_64.dylib. GNU/Linux test build includes baseq3/vm/ui.qvm so no vm_ui change needed. Set vm_ui to 2 to restore default behavior of only loading QVMs.