Okay okay okay, So got into CS:S by playing combat surf back in the day, so safe to say
I FUCKING LOVE SURF.I'm really bad at it but still.
Personally what i think makes a great combat surf server (If you where going down that route, rather than skill surf) is a plain server, made so its easier to surf but not too easy. The maps should be maps that reward better surfers and have cool secrets. A personal favourite is forbidden_ways_reloaded found here
http://gamebanana.com/maps/137826. And that's pretty much it. Maybe a store that rewards players with credits for playing on the server longer meaning it gives players a reason to come back and play more (And check out EgN) but that isn't really necessary.
I just really hope you guys get this right because if you do you've got a constant player right here :D
P.S with what JT said about the RPG element, i think that just over complicates things. I don't like them but hey that's my option so yeah :)