That's an enormous presumption! You're saying that even in the theoretical case that frontier research is halted but efficiency isn't, we could do better then the frontier and reach world-changing AI in 30b parameters at home-scale labs?! If that's true then we can just give up now: the world as you know it is going to end in around a decade and billions are going to die, there's nothing we can do. But I don't think that's true. Advancing the frontier seems to take a massive amount of compute, data, and parameters: miniaturization only happens afterwards.
If you're right then I concede. It doesn't matter what we do, regulations or not. But if I'm right then regulation can do something and in theory help bring a better future.