has anyone up graded theier toilet..there are some pretty nice modern ones with risers and such ...what will fit (compatible)?

I believe that that same model is still in production by Thetford. Or at least real close. The only issue I have with these toilets is their placement, but that isn't something that can be changed without major mods to the plumbing.

Oh yeah; It looks to me that making any major changes to the toilet type and/or location is pretty much out of the question because of the platform and the liner wall behind it. Take a look and you'll see what I mean. I'd say that the toilet was an original design consideration.