Act on will vs at will

Can it mean the same as 'act at will', like whenever it pleases one? Can you think of a context when 'act on will' could be used?

Solution 1:

The difference seems to lie in the specific requirements of the action implied by the preposition.

"Act at will" refers to the timeframe in which someone may act; i.e. starting at the moment of speaking, the subject has discretion to perform the action when they see fit. A restatement of "Act at will" might be: "Act when you choose to." "Fire at will" is a commonly-encountered analogous example.

"Act on will" seems to refer to the action itself. That is, the subject may act in whatever manner suits them. A restatement might be: "Act however you want to."

"Act on will" would be somewhat unwieldy, and not intuitive to a reader, but it might find use in dialogue.