
Aservan |
I don't know of one. Attack of Opportunity or Champion abilities specify the Strike action. Both Trip and Strike are attack actions, but I don't know of anything that lets you use Trip in place of strike.
The Trip property of whips (and Flails in general) has some perks for making trips, but still doesn't allow action substitution.
It's a cool idea for a future skill feat, but might be too powerful? I think it should be Okay.

Castilliano |

Funnily enough, Whips are in the flail group, so if you crit with you AoO Strike, you make them prone.
So it's there...kinda.
And it's nice if they move, you crit-trip, they stand up, and likely they still have to Step to get to you with their turn now over.
As you can perhaps tell from that series, Reach w/ Trip might be a tad to powerful to do w/ a regular attack, especially when Fighters start adding extra Reactions. Too powerful like it often was in 3.X/PF1.

HammerJack |

Honestly, it could be even worse. In PF2, move actions that provoke a reaction, but don't leave the square, like standing up, have the reaction trigger after the triggering action completes. That means that, unlike PF1, allowing trip as an AoO would allow you to retrip the enemy when they try to stand.