Honestly, I think the only way to effectively make this system work is to truss up mercenaries to look less scummy than mercenaries. You could make a force that's trained in police protocol, and hires itself out to enforce the laws already in place on colonies. I think it'd be a pretty cool system, honestly, but factions not bent on galactic domination have a tendency to stagnate, apparently.
I've been trying to build up SSS (AKA the faction that doesn't really do anything and isn't even really a faction) as a sort of low-key secret spacepolice but that kinda thing takes time, and I think to do the whole spacecops thing you'd have to have a faction that operates on the downlow to get around larger factions going 'we don't need no damn dirty spacecops'.
