Discussing Espeed bans:
Honestly, -ate isn't that difficult to deal with. But espeed is, and Dragonite is the most popular proponent of it. If you make it a "One mon can have e-speed" or "one man can have -ate" Everyone's going to run dragonite anyway (altarianite probably as well).
Basically, if you're going to decide between an -ate ban and an espeed ban, you should ban espeed because its impact on the meta is much greater than -ate is.
Almost every successful MnM team I have run into carries 2 or more espeed users. Hell, I carry 3 and I'm in the top 5 consistently on the ladder.
If we don't ban this move, everyone is going to build their team to counteract Espeed, and we won't be able to explore the depth of the meta as well. But without espeed, people will still use Altarianite, Pinsirite, Salamencite, and in some rare cases, Glalitite for mons other than Dragonite, Lucario, Entei, Zygarde, and Arcanine.
I really, really appreciate the hyper offensive approach we have to this meta. This is one of the rare metas where you can't 100% check a special attacker like manaphy with sablenite blissey because of tail glow and magic bounce. If you think something's bulky, there's almost always something that can break its bulk, and that's what I love. But Espeed limits teambuilding.
Technically, so does -ate, but limiting -ate to one mon like BH puts all the -ate stones (Salamencite, Gardevoirite, Glalitite, Altarianite, Pinsirite) into one pool and you only get to choose one of the five. That's even more limiting to teambuilding than banning Espeed would. Instead, by banning Espeed, you get a massive redistribution of stones to other, more viable mons like Boomburst noivern, Fake out / Quick attack Weavile (Kyurem not withstanding), Return / Quick attack Archeops, et cetera.
The only problem I see this creating is that it makes prankstermons and/or using banetite much more viable. Then again, this can be easily counteracted by using magic bounce stones like sablenite, absolite, and diancite.