Engineer spawn timer idea

It gets frustrating when the spawn timer disappears and you are trying to build your base in the heat of a battle.
Has it been figured out why it does this?

I had an idea for another way to implement the spawn timer:
Make a build queue.
The first construction is built instantly, then starts the spawn timer.
During this time the eng can spawn another item like a turret, but only the turret base will spawn. When the initial spawn timer times out, the rest of the turret is automatically completed.
during the time that the turret is under construction, the player can cancel his build request (handy if your turret isn't where you want it to be.)

The health bar can be used as a build status indicator. Constructions will start with full health once completed (shouldn't really change the current game play much, since it doesn't take much to heal a construction)

Walls might need a different behavior since they don't have health bars

I similar idea could be implemented with monster pets...Instead they start as mini pets and grow to normal size as they are "build"