Unless they fill it with outsiders and mercenaries, it will be useless. Though it will fill the pockets of several big players in the arms market, which is probably why Obama is keen on it.
Of course it will be a mercenary army, at least the forces the Gulf states delivers. The Egypts will likely use their own citizens. So I expect Egyptians and Pakistanis being the two biggest groups, while Jordani, Sunni Yemenites and Sunni Saudi Arabians (there's enough poor Saudi Arabians, that they're a realistic option) will make up the rest.
Of course I doesn't expect much of this force, it can likely kill off popular urban uprisings in the Gulf states, but against real armies (even Arab ones) or tribal militias, I expect they will do poorly. So it will serve well against increased democratisation of or giving rights to Shias in the region, but help little as a force in the civil wars in the region (Libya maybe excepted).
