Hanging from the front or rear wheel will still take up less space than hanging from the saddle, if you've got the height and light enough bikes/big enough guns to hoist them up there.
But if you can find roof joists/something you are confident you can whack some massive screws into to hold up a bit of 2x4 like your picture, then hanging the relatively light static weight of a few bikes is not a problem. You could then just put a few of these in from which to dangle them
Hanging from the front or rear wheel will still take up less space than hanging from the saddle, if you've got the height and light enough bikes/big enough guns to hoist them up there.
But if you can find roof joists/something you are confident you can whack some massive screws into to hold up a bit of 2x4 like your picture, then hanging the relatively light static weight of a few bikes is not a problem. You could then just put a few of these in from which to dangle them