A way to change bombers of both kinds into dedicated anti-building units!

They have a time to activate their advanced bombs, otherwise they hit the ground and don't do enough damage.

It sounds like you're trying to create the behavior of a tactical missile- Slow launch, easy to dodge, high direct damage. So why not use a tac missile? There's no need to fuss with bomber behaviors, not when anything in the game can destroy a defenseless structure.