I think that you will find that if you tilt the bucket down so the cutting edge is straight up and down, it takes up about the same room as raising it up unless you can raise it to highest level. If you wish to keep it up high, then buy some cylinder lock sleeves to block it so it cant fall. Install them on the boom cylinders as many as you need, then lower the FEL to rest on these blocks. Just remember that you have to raise the FEL, remove the blocks before you can lower it down. Oh, and those things aren't cheap either.
As for rusting the cylinder rods, just how long are we talking here, it takes a long time to remove the oil coating and rust thru the chromium plating. I have found that the biggest cause of pitting on cylinder rods is from iron contamination which causes rust to form and pit the coating. Normal storage of a few weeks or even months with rods exposed is not going to hurt it most especially if it is under a shed. We had no sheds to store our farm equipment and the disks would set with the cylinder rods exposed all winter out in the weather and we never had any rust on any of them, but they weren't laying in the dirt up against a pile of iron either. They were on the equipment at least 30" off the ground.