Once you gain a physical presence, you're now liable for both federal and state taxes (depending on where your location is). This is much worse than your 5% revenue share or equity fee.
Add to that any legal and accounting fees you've just added for the company in the US, and you're essentially giving up 5% for a whole heap of pain.
Keep in mind that most law firms already provide this service. And they don't ask for 5%.
Your "pain points" are also over-exaggerated. The only reason for a company to consider a US presence is dealing with VCs or if they want to use something like Stripe or Braintree. Both of those are expanding (or have already expanded) globally.