Just my two cents.
The HEMTT cabs are a lot heavier than I originally thought and it's good that I went with 5 ton axles and suspension to handle tha additional weight up front.
The spring packs can always have a leaf or two removed or the entire pack re-tempered if the ride is too stiff. Re-tempering ain't cheap, but it's do-able.
There are a number of COE cabs that are aluminum and slab-sided enough to pass for military with a coat of 383 green laid on.
As most COE cabs sit over the engine (hence the derivation of the term), a 'wind tunnel' is already there for cooling air flow as well as under cab insulation to keep cab temps bearable.
Just remember though that most COE cabs are two-seaters. So much for taking a third buddy along, or having yer sweetie sit close on that long ride.
As to why to do any mod? Sometimes just because it sounds/sounded like a neat idea at the time.
Once the rent is paid and the children are fed, it's a pretty innocent way to spend your time and money.
At the end you'll either have a unique vehicle-- or first-hand knowledge of why it didn't work.