Motor "power rating" isn't just windings, it is motor design (ability to shed heat, efficiency so it doesn't create the heat to begin with, etc). Given the difference in power level you are after, it's possible you'll need to start with a physically larger motor; just rewinding this one may be insufficient.
The "power rating" isn't really all that meaningful anyway; see this page for some thoughts on that:
"There's no such thing as a rated watt!" Read here for why we don't advertise a simple power rating for the motors we sell. Also, have a look at our Youtube video where Justin talks about the power to propel bicycles in <a href="https://www.youtube.com/watch?v=ALde6zhLPs0">"School of Watts"</a>.
ebikes.ca
If you have a specific job for the motor to do, it is better to determine what torque you need from the motor at what speed (or range of speeds), which you can then use to determine a specific kT (torque / RPM constant), which you can then figure out a winding for. You can possibly use the motor simulator here
Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...
ebikes.ca
to experiment with that. Be sure to read the whole page to get a better idea of how everything works and what to do with it.
Defining what job (speed, acceleration, etc) the motor is already doing for you, under what conditions (terrain, wind, weight, etc), and then what job it needs to do for you, under what conditions, will help you with this project (and will be necessary to use the simulator to figure things out).
To greatly increase torque you would need to alter the design of the motor itself, increasing the width of the stator and rotor (magnets) is the easiest and probably highest effort/benefit ratio.
Note that changing the torque constant also changes the RPM constant (kV), so to get higher torque you get a different RPM, for the same motor power. For instance, non-hubmotors can use a high motor RPM with a lower-torque smaller motor for the same output power, and then use gearing to convert that RPM into torque, for the same power (minus the efficiency losses in the gearing). (geared hubmotors do this, too, but with a non-alterable gearing ratio; middrives can easily have the ratio changed by the end user).
To get a higher motor power (whether you change the winding or not), you have to increase either:
--The voltage to the motor (which increases it's RPM unless you lower the kV of the winding)
--The current to the motor (which increases the heat generated for a specific winding resistance).
Either one will almost certainly require a different battery than you have now, and probably a different controller as well, since it's likely that either or both is limited by current or volts it can handle or supply to below what you want to do with it now vs what they were designed for.
