I know this is going off topic for EQ EMU but why not look into making your own game with your own engine. There are plenty out there. You mentioned tribes so I would suggest Torque. It will never compete with a MMO because of the network but if you are just designing a game and it is going to be multi player then Torque is your best option. Don't get me wrong EQEMU is great and without it I would have never thought in my wildest dreams that I would have my own EQ server but to add zones and such is just making a different game. Why not take the EQ client out of the picture to avoid legal stuff and go for something you can truely call your own. Here are links of several engines that are out there. Each has something unique to offer.
Torque
The Nebula Device
CrystalSpace
Ogre
There are more out there but those are the ones I looked at that have what I was looking for.
Hybrid Mode
