I see a problem, since the Rheinland Military is the Rheinland Military. If it was meant to be a subsection of another group, they'd call it something like "39th Schwarzealders" and it'd be led by a Kapitan, or at best maybe a Vizeadmiral. As of now, it's led by two Grosseadmirals (Fleet Admirals) and the Gottkanzler himself (as commander-in-chief).
I can see people roleplaying Rheinheer (Rheinland Army, stated by Robert to have NPC leaders) and Bureau der Marineintelligence (Rheinland's equivalent to the LSF) but not the Kriegsmarine (Rheinland Navy) itself.
A problem is also, what is an "Independent RM" independent of? Rheinland is a fascist militarist state, so there's no way he'd be independent of the Oberkommando (RMHC, in English). Even relatively liberal nations like the US don't have people independent of groups like the Joint Chiefs of Staff, so I don't see room for roleplay outside the Nord/sudkriegsmarine (Northern/Southern Rheinland Navy), which are under Grosseadmiral Krieg/Kaisers commands.