My suggestion is a new Anchor block that will transform all blocks attached to it into a contraption entity unless it is powered by a redstone signal. The anchored contraption will stay in place, even if the anchor itself is turned into an entity. If that happens, then the anchored structure stays in the same position on the anchor even when the anchor moves, while remaining a separate entity.

This issue has been marked as stale because it has been inactive for 3 weeks. It will be closed if it remains inactive for another 3 weeks.

This issue has been closed since it has been inactive for 3 weeks since it was marked as stale.

I think that it would be better to only turn the attached blocks into an entity when powered by redstone to be consistent with the minecart assembler, although this would require not being able to attach this entity to another that moves the anchor block (or making redstone work on contraptions)