Dota 2 has a similar mode[1] where you can't choose from your 40 most played heroes, although this is based on what heroes you've played previously, not the heroes that are most played globally.
I've been wondering if a MOBA could use a balancing algorithm, and tweak a pre-configured variable character stat if a champion becomes too popular, too high win ratio, or too weak.
Even more interesting IMO would be a stock market, where players can spend in game (or real) currency to manipulate the power level of their favorite champion. Over time, people will bid against overpowered champions and their numbers will get tweaked downwards. You might see certain champions that people consistently choose to invest in (to buff), but it will be an honest measure of the popularity of the champion and can be combated if enough of the player base hates it.
Basically, balancing is hard.