I dont really have an opinion either way but as I understand it this is why so many people are opposed to complex bans as you suggest:
People are opposed to banning parts of a Pokemon. Moody is broken on anything so Moody was banned. Swift Swim + Drizzle is broken with basically every Pokemon. However, Speed Boost is just a part of Blaziken. High Jump Kick also makes it broken. You could easily ban STAB moves on Blaziken and achieve the same effect as banning Speed Boost would. You could easily ban Dragon-type moves on Garchomp and it wouldn't be broken. You could easily ban special attacks on Kyogre and make it not broken. Correct me if I'm wrong, but I'm fairly sure this line of thought is why a lot of people are opposed to complex bans like you suggest.
I DONT DESERVE YOU