Oh, yeah, I can see what you're talking about. I knew someone that did something similar. They didn't cut the rockers out just did frame mounted sliders underneath. I stood on them once and was surprised how much they could move up and down with just my ample body weight. I figured the best way to do those would be to tie the 2 frame rails together top and bottom as well.
I guess it all boils down to having the best I can manage without a cage to tie it all together. If the price of steel does what some are saying, there's even less chance I'll ever do a cage in this truck.
I never could come up with a good way to mount sliders on the original bed. Although it just occurred to me you could tie the bed sliders into the frame since the bed itself is just bolted to the frame. MAN! I can't believe I never thought of that until now.
Another thing I've thought of, if you didn't want to cut the rockers out, is to just add a piece of 1/8" steel plate over the top for some extra armor.