They've already said numerous times that the FM will not be part of the Player Development Team's input. Maps, skins, ground objects, 3D airplanes, sounds, etc, but NO FM access.
I guess they could change their mind, but I don't see it happening as long as HS is there. IMO there's no reason why a SMALL team of "qualified," trustworthy community members couldn't do some flight modeling as well, but that's iEN's call I guess. They've been burned by some scumbags, and that's probably ruined it for the rest of us.
As for "hackability," ANY sim can be hacked. WB was hacked before, and AH is being hacked now, you can bet on it. Probably, most of the hackers here are being caught and quietly ousted, but the weak link appears to be NOT the player's FE, which gets checked, but the data stream itself, which may or may not be. That's how WB was hacked: gun data being tampered with to boost lethality.
Player-submitted additions only gum up the works if it's unrestricted, unmonitored, and not quality-controlled, i.e. the Microshaft Method
There was a lot of trepidation about even allowing TERRAIN to be produced by players, but that's working OK, isn't it?