The front axle can take the weight of the loader. If it couldn't the oem would say no loader is allowed to be installed on the machine. The filled tires and rear weight helps with stability.I love that my comment stirred up such a great discussion. I appreciate all the input and info and I'm definitely more knowledgeable for it.
So I've learned that the only downside that matters to me is losing the inability to handle a filled tire if I get a leak. That's a concern as I don't currently know of a mobile service for that.
Pretty sure I get the difference in weight at the rear axel and behind it. I would have assumed that the front axel could take what the loader can lift but that apparently isn't exactly correct...most likely an issue over time.
If I fill my tires it'll be with something non-corrosive, likely rutabaga juice... or whatever its called. I'm looking into home spun 3-pt ballasts or possibly adding weights to my BB. I doubt I'll buy a dedicated box unless I found a really cheap used one.
The filled tires really help with traction and stability during all uses. Like mentioned before, not all of us just use the loader, and when doing ground engaging work, you need the tractor weight to keep traction. Hanging weight on the 3 point doesn't do much if the tractor looses traction when pulling a plow, ripper, box blade ect.