To do this, we need your friction model, since it will affect when you hit your max speed.
That is, unless you're achieving your max speed by clamping.
Let's try that version first. It's a bit crude, but it'll at least give us a starting point.
Let's say we start at a standstill, and accelerate at our maximum force in one direction for t seconds until we hit our max speed, with no friction slowing us down:
If you want higher mass to make characters accelerate more sluggishly, you'll want to use one mass for calculating controlForceMagnitude (call it a standard reference mass), and then use the character's actual mass for the division.
For characters that have your standard mass, these two will still cancel out, and they'll reach their max speed in exactly the time you set. For a character twice as heavy as the standard mass, they'll take twice as long to hit their max speed.
It's a tuning value. It says "This is how heavy I expect my usual character to be"
Don't try to get rid of all your tuning values. Game design is about choices. You can't just abdicate every decision and calculate it from some physics constant of the universe. You're making your own universe, so you need to supply the constants. :)