F3WMB
I can see potential for confusion for the casual observer in dropping the designations (F), (AC), etc; if II(AC) were to become just II, it could be seen as 11 (XI) by, say, non-RAF peeps. But this is perhaps the only circumstance where it could happen (I can't think of any other Roman-Arabic numeral other than this).
Davef68
Whatever next? You'll be wanting flight lieutenants running flights and group captains commanding groups as well, I suppose. Don't you see how career-limiting this would be for the greasy pole promotion system.
Mister B