Possible, but that is worse than just creating a device for which you use a notifier to listen to its parameter changes:
I made an attempt creating a pitch device that responds to automation (it is frankly the same idea, but without the need of a route through a Midi controller).
It sort of works, but it sucks if you have a very slow PC. (scripts are running in the GUI thread and do not have real-time priority, so no matter which route you choose, it will never be 100% realtime)
You could perhaps make that device trigger the phrases API and it will work but if you really have to swap between having the phrase running on line x and stop running exactly on line x+1, this might stutter or cause other artifacts. (I have not tried it, but it is my suspicion)
Triggering something on or of has one advantage above sliding a pitch value:it happens less frequent than following a slider for a pitch shifter.