Given what little I've seen about SI's skill and expertise at managing the internal politics of such an arrangement, I would expect the current staff to be promptly displaced by more skillful politicians if they went down this road, and the projects of interest to that staff to end up with even fewer resources than they have now.

I think this has already happened to some extent. Reflective people who have good epistemic habits but who don't get shit done have had their influence over SingInst policy taken away while lots of influence has been granted to people like Luke and Louie who get lots of shit done and who make the organization look a lot prettier but whose epistemic habits are, in my eyes, relatively suspect.