I would love either to make a toggle option that would allow auto-reclaim/building on top of already existing buildings or a keypress that tells my constructor to auto-reclaim the buildings in the way of whatever I wish to build.
If I have a windmill-farm, but want an AFUS in some of the spot they're occupying, I would prefer an option toggle or a keypress that told my constructor to reclaim the buildings in the way for me to start construction without having to spend all my APM cleaning up the base.
Same kinda goes for replacing t1 energy converters with T2. If I could just shift+alt build in the same spot and have my con-bot slowly replace the T1s with T2s even though they're not the same size, it would be pretty great for my APM to be able to get rid of the lower efficient T1s easily if I see the game dragging out.
Losing frontline units due to having to spend too much time micromanaging building base that AI could be helping me with feels bad. I'm old and slow, but love the game. I feel like many are in a similar position to me in regards to lacking APM for this. I guess it mostly matters on smaller maps 8v8 where space is a limiting factor.