Are the TIM1,2,3 pins used for anything else? If not, BLDCDriver6PWM should work to get the timer running. The effect of PWM duty will be inverted from usual (lower commanded voltage will give higher voltage relative to system ground) but I don’t think it will cause any trouble. Unless you’re using lowside current sense, in which case I think it will trigger when the high mosfet is active.
I haven’t studied the timer registers enough to say whether it’s possible to run 3 inverted channels alone.