Billdelong,
I agree that the cup racer is not the best for the 1/12 (mini or true ten class ...whatever it is called).
I think it depends on what your club or track allows. For example one track I race at allows most all 1\12 cars (not pan cars) in their mini class, yet tamiya m03 and m05's are the majority. Their are a few cup racers that dominate. In another club in race with they are extremely specific and follow the tamiya championship series rules ....so tamiya M's only.
My preference in this class if everything 1/12 was allowed would be something like you are recommending or an atomic lipo (the price, qua?ity and performance are great).
My least favorite and what I consider to be a quite crappy quality is the tamiya mini cars. I own both a cup racer and a tamiya m05, the cr'r is hands down a better car. But the tamiya championship series is what made this class what it is and therefore the tamiya M's are still most common and allowed where others are not.
It is fun trying to get the tamiya to perform however.