Without saying I agree or disagree on the issue Agent Provocateur is aimed at, I suspect it might come down to opportunity cost (sorry for the jargon): printing a bunch of viable starting posse dudes uses up many card slots and could leave a set feeling useful but a bit vanilla, while printing Agent Provocateur is an interim solution that covers 80% (or whatever!) of the same problem but uses up only one card slot in the expansion. Then, you can add more reasonably priced influence options (if desired) in a subsequent larger set.
Sorry if this feels like rehashing part of my post above. As noted, this kind of thing is way above my responsibility level.
Linked to all of the above, interested in which factions people find starting posses particularly easy/hard to build for. Is there a feeling Sloane has a particularly tough time scrounging up influence, particularly with FMB growing in popularity and making Jake Smiley a significant risk?