We do this at York (
http://www.yorcc.org.uk/about/ )
540 Sealed Can Brushed (2wd) / 17.5T Brushless (2wd & 4wd). These classes are aimed at newer / younger drivers and those who want a slower and simpler racing pace (though the lap times after often close to some Modified racers). The 540 motors should be sealed can 20 turn brushed (eg HPI Saturns) in 2WD cars. 17.5 brushless motors must have speedos running in “Blinky” mode i.e. no timing advance or power boosts.
2wd Modified. No turn limit. Many drivers opt to go no faster than 10.5t.
4wd Modified. No turn limit. Many drivers opt to go no faster than 10.5t.
Short Course Trucks. 4wd and 2wd currently in together. No turn limit.
Works really well, both new and seasoned racers choose the 540 classes.