The idea isn't bad.
But main problem is the vast majority of players doesn't RP.Most halo players are into CTF,Zombies,Slayer game types.So most of the time the server might be "dead" and with that i mean empty. Gijs and the other admins are putting a lot of effort to keep all the servers up.Having one more server that might be empty most of the time would be a bit tiring to manage.
Especially with the type of players Halo has. Eventually someone who isn't used to play RP will pops in and starts shooting people.Not to forget that most of halo players are from 10-15.Then it would devolve into a mess of arguing.People might get annoyed or even mad and leave the server or even brake the rules of the server resulting the admins to take actions.And as we all know ,because of the number of servers {XG} has ,admins wont have enough time to take care of them there.
But in the end this is just my opinion so don't get me wrong.