I came across this thread too late and didn't get to see any of the pictures you guys did. BUT.... if there was a sufficient platform attached right at the loader, I would get into it but I'd have to trust the operator. I've seen how much bounce there is in a FEL, so I wouldn't stand in it while traveling more than a few feet at a time. Sometimes terrain can set up an oscillation in the loader that would probably throw a person right off any platform at all but the slowest ground speeds. It is real noticable in a bumpy pasture carrying a 6x6' round bale on the front and one on the back.
Take what you've got, and bring the platform up to the tractor as close as possible and beef it up. There are many uses in which this would probably be fairly safe, such as a ladder substitute..... but I wouldn't use it in a situation where something could fall on the loader.
When I was little, my dad and grandpa were cutting a 100ft pine tree down. They told me to get behind the tractor where "it was safe." Well, the tree as it fell dropped a large limb that landed right across the bucket of the tractor. The tractor probably weighed in at 10,000lbs but I remember seeing the rear end lift up several feet into the air before crashing back down. If there had been a person inside the cab, they would have had an amazing ride.