Entry door(s) and awning on passenger (curb) side.
Sewer, water and electrical hookups on driver (street) side.
I don't recall ever seeing a travel trailer that had the door and awning opposite from that standard. There may be some that have the hookups on the opposite side, maybe I didn't notice.
I certainly like your idea of building an all metal trailer. Should last several years longer than a wood trailer.
You may want to consider building the inside of a metal cargo trailer into an RV, instead of building the entire trailer chassis and body from scratch. Probably save alot of money.
If you build it from a cargo trailer that has a rear ramp door, you can use it as a toyhauler too, and can fold the ramp down flat and screen it in like a tent, as an add on room while camping. They sell those tent/screen rooms for toyhaulers with rear ramp doors.
01 International 4800 4x4 CrewCab DT466E Allison MD3060
69Bronco 86Samurai 85ATC250R 89CR500
98Ranger 96Tacoma
20'
BigTex flatbed
8' truck camper, 14' Aristocrat TT
73 Kona 17' ski boat & Mercury 1150TB
92F350 CrewCab 4x4 351/C6 285 BFG AT 4.56 &
LockRite rear