Precisely: the potential added acceleration due the increase in force would have to be counterbalanced by a deceleration: that is, a resistive force is required in your scenario. It is obvious since $P=cte$ means $v=cte$ which in turn means that your force F is balanced out by some resistive force.

Precisely: the potential added acceleration due the increase in force would have to be counterbalanced by a deceleration: that is, a resistive force is required in your scenario. This is case also when $F$ remains constant : then $v$ is also a constant, meaning that a resistive force balances out $F$.