The proposal is "Planned Construction", one of earliest green science techs. It gives you blueprints and deconstruction planner, and they require green circuit instead of red. With these you may place ghosts and plan big chunks of your factory ahead. You also get automatic ghosting of destroyed entities.
Now, whenever you run, any ghost item available in your inventory is automatically placed to nearby ghost as if left-clicked. Such semi-automatic construction happens only for character's rear hemisphere so you don't place furnaces or belts ahead of you, only behind with respect to running direction.
Semi-automatic deconstruction takes time to harvest every reachable item around the player. One by one. Character does not actually move until deconstruction is completed and releasing movement key in the middle of yellow harvesting bar stops deconstruction just like it currently works for right-click. Semi-automatic deconstruction time better be zero for everything except trees but I know people around here who would oppose such decision
Semi-automatic construction and deconstruction happens only when character moves, so placing a ghost next to you or marking something for deconstruction does not cause that to happen immediately, only when you move. That's to avoid misclicks.
It would be nice if ghosts have no timeout on them, so you may actually plan your factory ahead a long way. CPU cost of many ghosts is nothing when there are no construction bots, just some GPU cost due to transparency. And when construction bots appear, I can think of at least two ways to make them cost nothing on CPU as well.
This proposal if implemented will kill the need for personal roboport. But it's not so useful already for you may drop regular roboport anywhere, fill it with bots. get wider range. then deconstruct.
