If you know your way about the GECK you could always make a Faction replacer, plus it could be your own personal mod that you have. Not sure if the FO3 Enclave PA is in the files for NV but if it is you could easily switch out the NCR or BoS with (or make another Faction entirely). If all else fails though you could always use that good ol' Remnants PA.
As for a mod that replaces or add exactly what you are looking for.. your guess is as good as mine.
If interested though I found these VIA a quick Nexus search for "Enclave" on the NV Nexus:
- Mod 01:
- Mod 02: