Maybe it's different with new engines (but I doubt it), but you wrote, "...drop each piston in turn, examine the bores, and replace the pistons and rings from below if there's room...."

"...if there's room...." is the question. My experience rebuilding is with old push-rod engines, but (if it's the same, and I don't know why it wouldn't be) I don't know if you can do that from below. You can detach the connecting rods from below (you have to), and may be able to remove the piston -- but reinserting it from below is a problem -- remember ring compression, etc., not to mention any thick edge or lip in the cylinder down there.

Better to plan to pull the head and do your piston extraction and reinsertion from the top.