I have almost the same plan in mind for a new comp rig. Working on my chicken charcol pit now materials for trailer in garage.
That thing is stout. Excellent cooker and tons of storage... and big time pretty too. Great fab work too.
Suggestion for consideration
1. The space at rear... gas burner for beans or wok. Also space for duch oven cooker for potatoes
2. Where the tonge meets the frame it is well braced on inside with tubing. Might need a patch on outside say 3 inch x 3/16 about 8-10 inches to protect from stress crack later on.
3. Buy a super big chain and lock, keep it under cover maybe some pit bulls too
thanks for the pics, too! Best of luck