If the program were taxable, governments might allow less red tape; incorporating is not that hard compared to 501c3 formation. [No doubt you have some interesting 501c3 qualification stories.]
I suppose the biggest headache would be obtaining cooperation with most governments. This would have to be an international venture, obviously. [If we wait too long, we'll have to work with other planets. So we better address it now!
.]
As long as people from every nation are willing to financially support noble astronomy and space causes (e.g. saving Hubble), with the added benefit of having their name on a star, why not find a vehicle which would produce a means to this end. If astronomy wants to sow and reap more, better to use a John Deere than just the mules.
