It's hilarious how upset some people are in this thread that I simply am suggesting that a very useful ability have a cooldown timer, like you know, every other ability in the game.
It makes no sense that you can have an indefinite brace. It needs to have a cooldown timer so that there is a RISK to using it, not just benefits. I don't see how anyone could possibly argue against this. 1 minute cooldown for an ability that lasts 30 seconds is completely reasonable.
The trade off is that the building is not able to do anything. Think of emplacements for UKF is like regular Units for everyone else.
If you force the enemy to brace, then that unit/structure is out of play for 30 seconds. The offset is the same if you had retreated/blitzed out of the engagement for fear of loosing the unit.
Emplacements are core to the british faction, hence they have brace so they dont just melt under lefh/stuka/CAS/Luftwaffles.
Brace is fine and doesn't need a cooldown.