In my opinion a great program idea would be to create an equation solver for the 83+/SE much like the 86 (which could solve for any variablein the equation). A good example of what i mean would be to go to this website:
To solve equations like on the 86, just move everything on one side of the equation to the other so that it equals 0. For example, to solve 2x=10, move it over to make 2x-10=0. It'll solve that just fine.
As far as the other thing, that's what Symbolic is for. I'm pretty sure it simplifies things.