SMOKE, more thoughts

1. Limit smoke rounds: Good idea, bookkeeping pain. We don't track HE
grenades....

2. Say smoke takes one ACTION (not activation) to thicken up to acceptable
levels (hard cover). Otherwise it is soft cover. This means if you pop smoke
as your first action, by the end of your second action, it will be hard cover.
If you pop it as your second action, your opponent will get one action to
shoot at you while you are in only soft cover.

This probably fits within the timescale of the game (you can't really justify
it taking turns to erect a screen....). But it does take a time amount that is
significant if you are in the sights of the enemy!