If you want to deal with wheel hop, you need at least LCA's. I was getting a lot of wheel hop and this last weekend just put LCA's in and the wheel hop is now gone. The link for them is below and it's totally worth the 100 bucks.
As for a UCA, I havent done that but I believe that it would handle axle rotation which should ultimately help with wheel hop as well.
For the frame flex, you can get into stiffening, but I can tell you that my old mustangs had a lot more flex than the 06 and 10. That's why I dont think you need to make the frame more rigid unless you really get into racing it, and then it becomes kind of specific beyond my knowledge and skills.