First of all concerning the fees. If the Arena would be managed by taxes, you wouldn't be allowed to loot anything, and that's just pretending you did not kill your opponent. You loot things, keep the money for yourself. You kill animals, which are quite expensive to replace. The amount of swords looted in the Arena each day exceeds the smiting capacities of all the smiths in the vicinity of Hydlaa. If the Arena would be financed by taxes, the Octarchy wouldn't have much money left. Later, we'll also have season passes. We don't know hot to do them yet, as there's no time in PS.
Concerning the gladiators, of course they'll be mostly players. I detest NPCs. Gladiators are the Arena's capital. If you'd just let them be severely wounded by a person significantly stronger then them, soon, the Arena would be a large hospital.
The NPC assignment thing is just something I came up with, as it is how the Arena would be managed realistically. After all you wouldn't move through an Arena drawing your swords on any gladiator and beast you'd cross. You'd actually ask those that supply the gladiators/beasts wether they can spare them. As the Arena is primarily focussed on fighting, and not earning money, I'd say whoever comes first gets it. However, it'll be difficult to realize. And next, I did not say we'd evict anyone. We'll only assign NPCs "unoccupied" by persons. However we're still a good distance away from implementing that, the assignment of NPCs.
The guild will always be officially led by Gregori.