Barotrauma should be able to take up to 16 players and if you as a group can get into this game then you will have a good laugh for a good amount of time.
Golf With Your Friends - up to 12 p. Simple game but getting hit by your friends ball right before scoring the hole kinda never gets old.
Any grand strategy will be able to host many players Civ, HoI, HoMaM, AoE, RoN, Stellaris, …
Producing the “epic drops” steadily will require having separate factories for it.
To me that sounds like you are going to hit the UPS drop sooner then (?)
Ooh, opt-in makes a lot of sense with this, with that it can be considered as a kind of “increased difficulty” setting for seasoned, veteran players who want just something more to work on optimizing.
Even in the finish location, if any of the “law” fuckers scourging the open trackers, sends an abuse/dmca to Hetzner, you will have some explaining to do as they will raise it as a ticket and require an explanation as to what happened and what is your course of action to remedy it.
Source: my own experience about two months ago (used chatgpt to send them a neutral bussiness respone, worked like a charm)
Use vpn that allows port forwarding, or never touch public trackers at all, or both.