On Dab's ideas: I like the thought of pretty much everything you've suggested, with the exception of the troop landing scenario, I think that would be a pretty cumbersome and difficult thing to referee, though I do like the ideas of having to use transporters of some sort in full-scale war.
On Igiss's ideas: The "private" systems is a great idea, maintaining the original feel throughout the rest of Discovery. However, what you're suggesting basically makes these "private" systems exclusive to their owning factions only. What I mean by this is, say there is a system, off of Frankfurt, owned by a Bundschuh affiliated clan like you say. Now, if SF (Bretonian Armed Forces) successfully attack and win control of the system, then there is a BAF owned system off of Frankfurt... this makes less sense in roleplay than BAF taking one of the bases from the original game, and also causes problems with members of that faction travelling through other faction owned space in order to get there.
The only solution I can think of is something along the lines of Connecticut, a neutral battleground where all factions can stake a claim on a certain section, and base defence/assault battles can all take place without interrupting regular gameplay across the original systems. The system would in theory look like a regular skirmish map from a strategy game, bases around the outside of varying strength (depending on how much money the faction that owns it puts towards it?) with their affiliated NPC faction patrolling it heavily. Pretty much all of Dab's suggestions could be applied here without ruining any other parts of the mod.