I think the onus now rests on the factions that have been allowed this special dispensation to establish why they should maintain this power as it now stands rather than looking to expand it even more.
Quasi-house factions don't really come into it. The systems on the list are meant to represent the civilised hub of Sirius - the major trade centres, population clusters, developed planets - that kind of thing. Considering the systems are referenced on the forum, the shorter and more comprehensive the list the better until such time as we can get every rule somehow wired into game mechanics.