I think those are good.
Poses risk of replacing what you already have, which is already an existing concept (getting a different unit when you already bought a unit), so it doesn't introduce new metagame.
Free airstrike maybe.
Slowdown sounds bad. Doesn't damage resistance crate already slow you down? That at least has pro and con at the same time.
Becoming invisible completely breaks metagame. SBH spy already insanely changes balance, getting some other advanced unit invisible would be completely OP.
Free beacon may be fine.
Free rank upgrade already exists AFAIK (makes you require 1 veterancy point to rank up each rank), but is insanely rare.
Airstrike crate could be easily escaped from, even on foot. Doesn't sound that good of an idea IMHO.