I'm not averse to the rule change, especially if limiting total power is the aim of the rules. 8 mini cims ~= 6 cims.
The performance gain might not meet your expectations though. A tank drive will be better at putting that power to the ground (in a straight line anyway). When accelerating or pushing, the bot will "squat" toward the back wheels. As the weight comes off the front wheels, the force they can apply may become traction-limited, rather than power-limited. In a tank drive the front wheels and back wheels are chained together, so the weight distribution doesn't matter, but in a swerve drive, those front motors may spin uselessly.
The math on how big an effect this is is left as an exercise for the reader
