Hows about some rollover protection too? The local guys thought my built in cooler mount was cool , when I started hitting the trails with them. They are big beer drinkers, and prolly do more drinking than wheeling so the cooler I chose would prolly be too small for their needs.
Mike wanted a basket after he cut the back of his runner out. It is great for the small stuff that you just need to toss somewhere, kinda like your toolbox, I guess. We used the larger expanded metal that you can easily hook a strap, or bungee to to tie stuff down.
Some sort of spare tire mount would be a good idea as well.