Well I think a base with the .50 cal gun would be pretty elaborate, though not much more than the Tony Start mech arm base.
I'd want to see it come with a clean t-shirt and headsculpt so you could have this look.
And then a BD headsculpt and shirt for his battle look, and I'd really like an alternate costume to have his going home look to mirror the M65 figure from First Blood.
As for not buying Rambo unless it's from IV, I'd get a Rambo 2 or new First Blood if they did it just because they look pretty out of place with M65 and Rambo 3, though with today's quality M65 and Rambo 3 would probably look a bit out of place with a newere figure, but I think less than the current contrast.