I have a 16' bed trailer. No dove tail (the next one will).
The ramps are ~5' long and slide under the trailer. The frame for the slide is simply two pieces of angle iron attached back to back (picture a straight Z) per side of the ramp. The ramp stringers C channel (look very much like yours).
Works ok until you have a low clearance vehicle, as the approach and departure angles are steep. I just purchased some used angle iron and 16' 2 x 8's. They will end up being ~12' long for my wifes skid steer and for my Miata (I hope they are long enough for the Miata). My bed height is ~24".
They will have some sort of 2x framed stand to go ~midway up the ramps to support them with a load (both are in the low 2000# range).
You will want to keep a block of wood handy to place under the trailer tail (a couple of inches short of how it sets when it is empty). I have learned this after loading my TN55. I got it part way on the trailer and noticed that the ground was moving regardless of how hard I pushed on the brakes! After I collected my wits I moved forward pretty quick to get some weight on the tongue. I keep an unsplit log around now.
I like the tilt idea, but I would worry about other items in the load (using the tilt pretty much means it is a one item load) moving off as well. I have seen dovetailed trailers with a raisable center section (making it a fully useable flatbed as well). I will be monitoring these as well as more conventional dove tails. Dovetails lower the approach/departure angle and allow for shorter ramps (I will also be considering the pivoting ramps).
I use my trailer for hauling wood and hay, so it still has to be a flatbed. The toughest part is that I want it to be a bumper pull -- and at least 20 foot bed (including dovetail). And cheap. As the saying goes, pick 2! Nothing wrong with using what you have and watching out for the right thing. You can only think these through so far until you have to use it and figure out what you really needed.
Oh, when/if you install lighting, add in a set of Wallyworld $20 clear fog lights as back up lights on the trailer. Man they make it easy!