Dave,
One very important thing to keep in mind is the trailer in your picture looks to be hot dipped galvanized at the factory. Simply cutting it apart, designing the tilt mechanism, etc…is one thing. Trying to get proper penetration and solid, non-porous welds with all that zinc is nearly impossible- no matter how much you try and grind it off before hand.
AND, even more importantly, the fumes from welding zinc are extremely toxic, (I found out the hard way…)
It’s a great idea, but, I’d steer toward the direction of an already built tilt trailer.
Just my .02.
Good luck!
Don