TCS rules allow brushless 21.5t motors, yes many of us and certainly those who race their minis like I do run a brushless and lipo battery setup.

I am using a Revtech Killshot "High RPM" 21.5t motor w/ a speed passion esc and shorty pack 2s battery (4500mah and 90c).
Some guys switch out motors depending on the track, shorter track w/ more turns you may want to try a high torque motor for quick start/stop acceleration. Whereas a longer track you may want to go w/ a high rpm motor for higher top speeds. The differences are sublte but very noticeable in a race setting w/ other drivers of equal skill.