Hmm...
Alchemist:
Poisoning as an immediate action probably could be done with the current PnP poison system. Using itemprops seems to force you to spend the rest of the round hasted, but you could have a number of control feats like "Use Nightshade" with subradials of "Use Nightshade: Mainhand"/offhand/arrows/bolts/bullets and just give that an activation time of 0 and you're good to go. They'd have to be added to your hide and taken off when required like the prep spellcasters, but that's been done before.
As for crafting alchemical stuff in a round, simple stuff that has no parameters to set could be done with control feats, or, failing that it would have to be done via quickselects, so you'd have "Craft quickselect 1" that you could fire off in combat.
Cavalier:
Unless I'm mistaken, switching class skills isn't something that would be terribly tidy. It's not really significant though.
Edicts would have to be down to module builders, except it's possible to throw alignment restrictions on some of them.
Some teamworking feats could be done by sticking stuff into existing scripts, but indeed a lot of them won't be possible.
Gunslinger:
I don't believe it's possible to check when you actually score a critical hit (unless you want to do everything through prc_inc_combat, then you can). I'm not sure what the swashbuckler uses to do its stuff, but that could be modified.