Do you already own the tractor? If so, go measure it, WITH a bale spear or mower on, so if needed, you can leave the implement on and just park it as-is without detaching it. Make sure you allow yourself some “wiggle room” - make the space a bit longer and wider than the measurements.
We have a 45hp New Holland with a FEL. It fits perfectly in a 11’ wide x 22’ deep space with the bale spear on. 22’ isn’t enough to park it with the 6’ mower on, but we can drop the mower at the back wall of the shed, detach it, and then park the tractor with the FEL resting on the mower.
If you are wanting all your tractor implements to be under cover, you need to take into account how they are accessed. You can’t just stack them in like dominos or you won’t be able to access them without moving another one.
You can always stack the bales higher to condense them… We stack a hundred 70lb bales SEVEN high in order to fit them in our hay shed. Builds muscle.