do note that it may about double your save file sizes
so it'll go from tiny to slightly less tiny, but still tiny
Up to almost double the size in lines, but very unlikely.
Ownership is one line, however, each event is also it's own line, item, vehicle, music, etc all have their own line.
So the closest ratio you could get linecount wise, would be a colorset with 1 color, build everything on top of a single baseplate, and use nothing but bricks. No events, items, lights, etc.
But since you said filesize, then it becomes significantly less than double. As each ownership is only going to be 13-16 characters long. (this includes the newline, range is based on number of digits in ID)
But yeah, when it comes to uploading a save to a server, line count is likely more significant than file size. That is something you'll notice for sure.