Endoperez: Good luck with that.
IIRC, the only unique units (or commanders) that RoR Caelum gets are the Raven Guard (not worth it), their 'balanced' Seraph, the Harab Seraph, and Harab Elder. You could give them all stealth and IMO not change much. (It would be nice if you could have stealthy Death mages summon up stuff to attack an enemy province they're in.)