I think you should have more than 4 tie downs on the trailer. I know the trailer I have now only has 6 and I use every one of them. My trailer also has a round tube running across the very front of the bed. I like this because I can power bind my loads ( if possible to)
It also makes it nice because it kinda gives something to stopyou incase you get out of control.... Althought that didnt stop the tractor from going up and over in tothe tailgate. grrrr I do like the dove tails also because I dont always have to screw with ramps when loading certian things. My jeep I can just drive right up on.
I do like the jacks in the rear, and make sure the front one swings because I have caught mine on alot of stuff and bent the hell out of it. as for storage, One of my trailers has it under the deck, this is nice because it is out of the way, but its kinda far down. You can never have enought storage though.
I have never had a plywood deck trailer it always has been 2x12 and the way they bound them down is they made it so you slide the front end under a peice of angle iron and then the back end you welded the back angel iron over the boards. worked quite well and nice.
Also I can see a problem with running the wires in side the frame, what if they needed repaired... it can possible be a huge pain.. just a sugestion.