I have a simple way to find out which winch is suitable.
Sail Force = v*v/80 kg where v is wind speed in knots. Normally for winch selection 50 knot wind speed is to be used. But you can use any speed you want.
If we assume it as 50 knots then Sail Force came out to be as 31kg.
Then calculate the sail area by taking into account for which sail the winch is to be used.
Sail Area x Sail Force will give you the Max Force which your winch needs to tackle.
Assuming by your arm you can only aplly 15 kg force and by dividing Max Force to 15 will give you approximate Power Ratio of the winch required.
GR= Gear Raito of winch
L=Length of handle to be used
So if you can find Gear Ratio and radius of winch it is easy to decide.
I appreciate your formula, but the key is the gear ratio which I can't seem to find published. I'm specificcally looking for the ratios for a Barient 22. Do you know a source where this could be found?