But with Dragon's Den being a thing why would you want to stop at 50
Most everyones story liners should be around 50 or 60 before the reach dragons den anyways so I dont know that this isnt a reason NOT to have a 50's meta. Although leveling isnt hard, leveling 7 gengars to 100 with different move sets isnt exactly what id call a good time either.
According to the previously mentioned ruleset, you shouldn't be leveling 7 Gengars anyway.