Add a fan will be easy and cheap method, can also cut few holes on the body near motor ..
Driving style will affect too, such as less hard braking..
~ 2000 - 2200 kv motor will help for sure, and you can still keep similar top speed, let say 2500kv motor with 15T, vs 2000kv with 18T, similar performance, but lower temp in general.
Or you can get a 1700-1800 kv motor to run 5s or 1300-1500 for 6s ...