[NaS]

The idea is good! But it has to be made very good, scripting-wise AND game-wise, it may also confuse some players.

1. Performance. Every mode needs its resources (CPU/Net) which could get critically with many modes.
2. Having too many modes wouldn't be good either, I would not include more than 3 or 4 modes.
3. Every single mode must be good. Else the players could also just join different servers or one mode is extremely focussed.
4. Managing/Maintainance. A bug caused in one mode can affect every mode (and even do rly weird things not expected). Also, you need a good admin team which you can trust, because it's impossible to manage all the modes alone. Even with a team it's going to be hard!
5. Advertising. Most servers fail because they do not advertise enough, or the wrong way. Or at a wrong state of development.
6. It could happen that the community is split up. RP Players trying out some DM will most likely not go well with DMers. The other way round too, ofc. This goes to managing as well. Without a good managed forum you will most likely get lost in a mess.

I would not add a RP mode. A Freeroam/DM/CnR would be doable, but the RP mode would definitely not be able to compete to other RP servers available out there. At least not in 1 year, since you most likely will loose interest after some time, or at least you won't be as motivated as in the beginning.

Dont get me wrong, not trying to destroy your idea, but I'm just giving you an advise.
A TDM/DM/CnR/Stunt server would be going very well. The modes should be compatible.