Great idea with the hidden wiring. Just make sure to smooth out the blind transition holes before you weld it up, to avoid wire chafing. Where possible, rubber grommets should be used. You're making significant progress on a large undertaking. Many kudos for you.
Thanks Vince! As mentioned earlier I really appreciate feedback. I hear you on the chafing issue. I do plan on putting grommets where I can. I also plan on covering the wiring in electrical tape and then an expandable cloth type cable sheathing as well and then zip tying it all together.
Something similar to this.