I'd suggest ovalizing an oversize top tube , laying the wide aspect horizontal.

to cure the tail wagging the dog syndrome
of my Specialized Expedition, common round tube, there was always
a bit of a wiggle with every pedal stroke.

so i got together with a cargo bike builder, who used 2 3/4x.049" wall tubes for the rear triangle
and the top tubes..
we stretched the design a bit and made a sloping top tube frame out of them
wits 2 700-40 wheels..

no tail wagging with that, BUT it is a rather heavy Bike, Steel Bruce Gordon racks moved off the SBI.
but as a loaded touring bike it worked quite well.

some weight savings by using the tube shape to get some rigidity laterally. seems practical.

could use same tube to form the downtube, rotated vertical axis..

But maybe the OP has only a light sport touring bike in mind, [then nevermind]
my favorite rides were show up at an airport unpack , toss the carton and ride off..
then look for a book sellers shop for a map ,
and decide where to go next day..
ride eat drink sleep repeat.. maybe find some musicians to play with.

tent sleeping bag and clothing for a cool spring thru fall aboard.