Maybe I'm a few years late to the party, but I don't think I've come across this mod before. I seem to recall the original idea for Generation Arena's "Resurgence" game mode being more akin to the old "Hunt" mod. That is where the new Arena Gladiator's BFG comes from, after all. The "Entity Plus" mod looks to take that to the next level, with enemy patrols and zones, triggered doors and events, usable items (like keys), opening cinematics and voice overs, end level stats, Q2-like mission prompts, etc.
There doesn't appear to be a lot in the way of maps for the mod, but the idea is astounding. Even the two demonstration videos are pretty impressive for what it is. Without yet having played it myself, the only thing that looks off is the enemy behavior. It's clearly using the Q3A bot AI, which seems to result in a lot of sporadic and outright aggressive movements that work fine in the arena, but maybe not so well in a more linear room-by-room style. As I recall, the Hunt mod did a decent job of having different behavior (and sizes!) for the enemy types.
I know it's a looong
way off, well after the inevitable 1.0 release even, but Resurgence as an idea always held so much potential. It's hard not to feel a rekindling of excitement when seeing something so similar being implemented elsewhere.