I would also prefer a cooldown. It would also make it easier to take when you're running to a point with your veteran and one of your teammates runs you over because slightly changing direction takes too long.
what stops people from waiting for the cooldown and do a big push anyway? a preset veteran sounds a good idea.
Hm yeah, it depends if the cooldown starts when you die or when you use it. When it starts when you die with the veteran, the Cooldowns get asynchron. You could still wait for a big push with everyone, but you would sacrifice some time where you have it ready, but don't use it.
People are forgetting you're going to need Tokens to use Veterans in launch(at least that's what I've heard). Depending on the cost, you may really only spawn those on the most dire of circumstances, at least at the start.