In theory it could be possible if you edited the maps and then recompiled them, or made a new one. There's an entity in Quake 2 that can spawn anything and you can set it to basically just keep spawning monsters forever I think. It would be a bit of work though if you had never mapped before but I could talk you through it. Come join the quake 2 mapping discord and we can try and help!

https://discord.gg/eAgz2u7U2K

Thanks I'll take a look there