Flatbed tips, tricks, wish list

I'll be needing an 84"x 12' flatbed soon for my new truck. I'm not finding anything specific that is better than anything else locally, and all are priced such that I can buy the materials to build out of aluminum for what most are asking for steel. That gets my gears turning towards building it myself.

With that in mind, what features or options should I be looking for or incorporating that I don't know about? I'm already budgeting for 60" of underbed toolboxes ahead of the axle and 48" behind. I know I want stop/turn and cargo lights on top of the headache rack, e-track down both sides, stake pockets and rub rails. I also lean towards the center 49" being dropped as close to the frame as possible, like a tow truck, so that it acts like a pickup bed. I realize that would negate some flatbed utility, but some sort of wood box could set in the center if I need it flat and the rest of the time I wouldn't have a huge void under the bed not doing anything except maybe hiding a gooseneck ball I'd never use.

So, what else? Air tank in the bumper? Loading ramps? Awesome spare tire winch ideas? Crazy cool bumper schemes? What have you seen that I can incorporate?

Edit: The top of the truck frame has a flange on each side with six pairs of mounting holes per side. In addition the end of the frame is set up with four reinforced through holes on each side for adding frame extensions. The end brackets are meant to be rigid but the upfitter manual calls for flexible mounting to the top flanges to allow for a little flex. Since the spacing on the bolt hole pairs is exactly right, my plan is to use 12 GM transmission mounts for that attachment. Anyone think of a reason why it wouldn't work?

Get some grade 10 metric nuts and bolts, as well as some kind of aluminum channel. Bolt the aluminum channel to the edges of the flatbed with the nuts welded up underneath, cut out D-windows all the way through the bottom of the channels and the flatbed frame that are big enough to put tie-down hooks in, and make panels that slide into the channels and bolt in place. Now it can be a box or a flatbed depending on what you need.

No input, watching with interest. A flatbed is usually step one of my off road truck bench builds.

can you do a dovetail? i saw something about shopping the transit van cutoff or whatever the cab only version is called to build an opel hauler out of. so if for car, dovetail the back.

Two or three winches under one side and LOTS of hooks.

Definitely winch, definitely a cherry picker arm (through which you can run the winch cable as well).

Definitely recessed/flush ring tie downs. Definitely a channel on each side with truck tie-down ratchets like on 18-wheeler flatbeds. If possible, a couple slide-out ramps under the bed.

Stake pockets in case you want to carry something that isn't self-contained. Or I like the hinged sides that fold down. You could just pin the hinges so you could pull them off in a jiffy.

And E-track. Miles of E-track.