On the topic of species clause, while I think it's a good idea, I think it would be better to, similar to the ability clause, limit it to two of the same Pokemon. Two Chanseys is hardly broken, as by the time you get around to fillling up the holes in your team with an anti-PH for both sides of the spectrum, a Gengar counter, all the while including necessary things like a bouncer and various support moves such as defog, you find yourself with little space to add to the rest of the team (Also
Whatwasthatnoise made a fair point about those teams just switching to Blissey). The real reason I think that adding a species clause would be a good idea is for teams that only consist of 5 mega mewtwos and an imposter that basically rip you apart if you only have 1 general counter to said Pokemon and win or lose on team match-up. Hell, even 6 Mega-Gengars can get you somewhere on the ladder, as shown by
TheBurgerKing99, who was able to get to the top 10 on the ladder using a cookie-cutter team.
My reasoning for making it a limit of 2 instead of 1, however, is that teams with say, 2 MM2X's are actually strategic compared to the teams that use 5 or 6 of them. The teams with 2 of them actually have a goal in mind: To have one of them weaken its counters so that the other one can sweep, all the while having a team that doesn't decide the game on team match-up and can be viable otherwise. It also doesn't eliminate things like Imposter + Unaware Chansey for example which would have almost nothing to do with the intended purpose of the clause in the first place.
Thoughts?