Just too add too the discussion about regestries, ISC ships actually used "Exclusively" Hull restries instead of nemes. All their ships identifications where completely based on hull regestries... their ships actually had no offical names assigned too them, but the crews themselves made up their own names of their ships. Also, I believe the Klingons only offically named their Small Gun Boats/Police ships by Hull Regestries (they made tons of G-2s' that they would probably run out of names soon). Also, I thought I heard once that most navies did not name their PFs' (if they built them) with names, just identification numbers or hull regestries (again, lots of PFs' around)
As for the Romulans, I don't see why you couldn't post Regestry Numbers. Their is nothing in Trek that is against it that I know of (not even in SFB).