I realize that some people are bothered by what appears to be a slippery slope argument that people are making about Blaziken. The main problem in my mind is that it isn't even a slippery slope (i.e. "this argument will necessarily be extended to justify things we don't want"); you can use the EXACT SAME argument the justify re-tiering a bunch of different Pokemon/ability combinations right now. Do we want to have a suspect test in UU for Damp Politoed, Flash Fire Ninetales, Sand Force Excadrill, Overcoat Reuniclus, Rivalry Haxorus, Sturdy Magnezone, Illuminate Starmie, Unnerve Tyranitar, Shell Armor Cloyster, Heatproof Bronzong, Zen Mode Darmanitan, etc. (not that I think all of those would be UU, but all of those Pokemon are enhanced by their current OU abilities). I don't think anyone wants to go through all that testing for every Pokemon that's significantly enhanced by its ability.
People are troubled by Blaziken because they're used to it not having Speed Boost, and being UU because of it; it's hard for people to wrap their minds around something getting a new ability, and suddenly becoming a whole different Pokemon (especially one that's relegated to Ubers because of it). But those people need to understand that, from everyone else's perspective, that's no different than saying "we'll allow Kyogre in OU if it gets Truant". We don't want to have ten Pokemon that are all split up by tiers according to abilities. But if we apply the logic for one Pokemon in one tier (Blaziken and splitting it so "not all of it" is in the Uber tier), there's absolutely no reason for us not to allow it with another Pokemon in another tier (Ninetales and "splitting it" so not all of it is in the OU tier). And, quite frankly, that's something most people don't want. We strive for logical consistency in our policies; if we say that we can split Blaziken but not other Pokemon, we throw any claims of logical consistency out the window.
People are troubled by Blaziken because they're used to it not having Speed Boost, and being UU because of it; it's hard for people to wrap their minds around something getting a new ability, and suddenly becoming a whole different Pokemon (especially one that's relegated to Ubers because of it). But those people need to understand that, from everyone else's perspective, that's no different than saying "we'll allow Kyogre in OU if it gets Truant". We don't want to have ten Pokemon that are all split up by tiers according to abilities. But if we apply the logic for one Pokemon in one tier (Blaziken and splitting it so "not all of it" is in the Uber tier), there's absolutely no reason for us not to allow it with another Pokemon in another tier (Ninetales and "splitting it" so not all of it is in the OU tier). And, quite frankly, that's something most people don't want. We strive for logical consistency in our policies; if we say that we can split Blaziken but not other Pokemon, we throw any claims of logical consistency out the window.