Change conveyor belt type while it's still a blueprint

Sometimes you build the wrong belt by accident and you took some time in doing all the routing. Then you realize it's the wrong one and you have to delete everything. It would be nice if you could switch the type while it's not build yet.

it would be nice in general to have both update/downgrade option on both blueprints and already build structures.

If it isn't built, we should be able to downgrade or upgrade belts, pipes, and buildings (for assemblers, if they are building something that requires a certain level of building, give a message that you can't downgrade further).
For downgrading, if it is built, then it should be treated like vehicle recycling... Bulldoze the structure, have vehicles remove the materials (or use Unity), Add the downgraded version, vehicles bring the parts (or use unity) and now you have a downgraded pipes, belt or buildings.
Blueprints placed over existing structures should Flag structures with a different tier as starting to upgrade or downgrade in a paused state and should paste the settings for balancers, buildings, etc.