|Tyrus, picture from GW (mine still being in a box)|
Leaving out psykers for now, think about a range, from Gideon to Tyrus, behinds the scenes string puller who relies on a combat team for action, to in your face power armored brute. Each has a range of personal combat power, from the feeble old woman who investigates through books and agents, through power armored chap who burns and punches his way to what he wants. Each of these supplements their skills with a retinue, and probably more interestingly for a tabletop game, augments their personal power with the combat power of the retinue.
Not retinue in the sense of all the forces they could muster, because Inquisitor Lords and older inquisitors often have a lot of resources and allies to call on, but retinues in the sense of the core group that an inquisitor would take to meet another inquisitor... or possibly to raid another inquisitor's domicile in a smash and grab raid. In either case, it seems like an inquisitor is trying to reach a certain level of power to bring to bear on a situation, and the physically frail one is going to bring more firepower to compensate for their frailty, and a powerful individual is going to feel more comfortable without bringing an indentured space marine with them. Both are perhapes equally likely to call in powerful allies for expected battles.
Psykers confuse things a bit, but you could see it as being part of the same scheme, where powerful individuals need to augment their power less (and perhaps bring more physical operatives), while weaker individuals need to bring out the stronger assistants (such as a psyker pet).
In any case, it seems like the "medium" Inquisitors, i.e. those who do some of their own investigations, but are more subtle than the power armored burninators, might actually have the more interesting retinues. They might have some powerful band members, but could also feel comfortable including more savants or researchers of moderate to negligible combat utility. In my own (slow) work, I am working on creating a bit of a range in the power of inquisitors and supporters, but it keeps hovering around the middle, where I think the interest really lies.
What do you think?
Related to these musings, I have set up a new Pinterest board that features Inquisitorial Warbands. it is pretty empty now, but I am trying to round up good shots of all the various inquisitors with their retinues.