Ask sama: E2 Visa?
As an attorney I have practiced immigration law, though mostly limited to cancellation of removal and asylum. However, based on your blog post, the E2 Visa can and should meet most of your requested requirements. The E2 Visa is a non-immigrant 5 year Visa with unlimited extensions.
In short if YC were to create a funding entity in the home country of a foreign national, and meet the "capital requirements" on a case by case basis (note there is no capital minimum, just vague criteria that must be proven, which YC would be in an ideal position to prove simply based on the nature of YC's experience and existing data), there is no reason this Visa should not suffice and give you supporting data of your claims while you continue to lobby for legislative change.
If you have already discussed the E2 with counsel and been dissuaded I am curious as to why E2 would not meet the needs of YC, because believe that this model in and of itself is a potential startup that solves the problems of other startups, namely YC and other incubators looking to fund more foreign nationals.