Hi Edemon and
to the forum.
The following 3kW and 5kW bikes from the GM website are both air cooled, but the larger 10kW motor below is liquid cooled.
Air cooling will be the lightest and simplest option as it does not require the additional pipework, radiator and coolant pump etc..
5kW should be ideal for your proposed use but if you need more power, check out the 10kW bike below.
See the above bike in action on
YouTube.
Further details can be found on
the manufacturer's website.
Here is a short video of the above
10kW bike in action.
Details of the 10kW liquid cooled bike build can be found
here.
I think you'll find that the above GM BLDC motors are all axial flux motors.
Alan