You're making a substantial assumption, which is that startups look for tax incentives when founding. Since nearly all startups are unprofitable for a while, I suspect that most don't really care what the tax codes in the area are, as long as they aren't ridiculous (insert your version of this accordingly).

I feel tweaking tax codes to encourage startups won't have its intended consequence, but rather encourage established companies to try to pretend that they're startups. They are much more likely to have the resources to chase tax incentives than a real bootstrapping startup.