I think adding this victory condition would make the mission far easier (I think it's easy as it is, but I mostly play veteran only), but if I would add this condition I'd also add a reinforcements timer; but we already have so much missions with timers that it could be bad for gameplay variety.
My course of action would be that: the old elimination-style mission remains (without pickup 3 soldiers condition), and new "bail out soldiers and escape until reinforcements arrive" is added too, but only one can generate per playthrough (with 50/50 chance)