Things only get slightly better in Codex Daemonhunters with the addition of another elite slot - the daemonhost.
And things aren't entirely as bad as they appear as Inqisitors do get retinues (another quasi selection) and can take land raiders as transports both of which fill in a few more points. If you can find a tournament organiser that allows forge world vehicles and further lets you take the IA2 updates to the Inquisition vehicles to bring them up to date it helps some more.
I've been thinking about this post and can see why you and others prefer Sisters & Grey Knights codexes without the Inquisition. If you're primarily interested in building something around the Chambers Militant then the Inqusition selections add very little and perhaps just dilute the army build.
Unfortunately if you're interested in a radical force then you're fairly poorly served. I guess my drive for a single Inquisition Codex is that the current Witch Hunters & Daemon Hunters ones pretty much just duplicate the entries I'm interested in (apart from some wargear differences) and so, from my perspective, having them split doesn't add anything.
I tend to agree with you that the Inquistion components are more likely than not to get restricted further and suspect that the only way to build a radical force may end up being to go guard and take a Primaris Psyker to represent the Inquisitor.
The radical path is definitely becoming a difficult one.