Makes sense, and I don't have a pruned node - mine's a start9 thingy in my closet and its full and getting close to full full - but doesn't this just mean that the solution is to save any blocks where you made a transaction? And pruned nodes already are waiting some number of blocks before pruning, so new transactions aren't impinged.
It would be more elegant if we could just prune the op_return, but alas, its the whole block.
