First the generator garage issue: My welds are strong enough to trust
my life on when I ride my recumbent trikes and other vehicles that I
have built over the years.

I'd feel better about it if you have a flexible section near the generator.
If your construction is entirely rigid then forget it, it will eventually
break no matter how good your welds are unless it's *extremely* short. Is
it a threaded connection into the engine? That's a good place for a break
if the vibrating engine is rigidly connected to a lengthy pipe. That condo
emergency genset you mention...if it was indoors it surely had some sort of
flexible pipe connection. Does your engine vent the crankcase back to the
intake? Finally, a decent ventilation fan either bringing in fresh air or
exhausting inside air, with either a vent or window that will be open
during generator runs to allow for circulation is a bare minimum. Then
maybe.

Is this gasoline or NG? Where is the tank vented? What about spills on
refueling? So much simpler and safer just to take the thing outside. Then
you can tell everyone about how you will hook it up via the A/C disconnect
box.