....I'm a homebuilder, and built a couple of tadpole trikes, and a LWB, and have to say the LWB is by far my favourite ride of the two. Not that there's anything wrong with the trike (biased I know), it's just that the LWB is more suited to the local terrain round here - much easier to thread your way through the rough stuff, potholes, rock strewn tracks, crumbling tarmac, cow droppings etc. The trike will get used, it's great fun, just not as much as the LWB, and I still ride a MTB - good to have some variation.
The AZ Warrior looks a close match for the OP's initial choice. My seating position is much more upright, about the same as my car seat I think. The laid back position would suit good road surfaces where speed might be the main objective, but I think more upright suits rougher terrain.
Having the skillset is only part of the battle for the selfbuild route - availability of materials, doner parts, welding consumables - they all must be considered. The AZ gallery is testament to some very fine results from the available plans, so it can be done...........