Re: 'hidden' upgrades from the factory build?
"The only dumb questions are the ones you never ask."
I'm on several brand-specific forums as we research our full-time coach. We're not going to by new, but we're learning quite a bit about what is available on various RV's. If we were in a position to buy new, we'd definitely ask the dealer to check with the factory on some things. One of my pet peeves, for example, is putting a pair of 6000 pound axles on a trailer with a 16,000 pound gross weight. Yes, if 25% of the weight is on the pin, then the axles support 12,000, so each axle gets 6,000 pounds. In practice, it never seems to work out exactly like that, so I'd order the trailer with two 8,000-pound axles. That way I know the axles aren't overloaded. Those axles might not be on the options list, but I wouldn't be interested in buying a trailer without them, and I'd make that clear to the dealer. No axles = no sale.
The dealer is (or should be) your friend in the purchase of a new coach. If the dealer can't or won't put forth the effort to get your coach built the way you want it, then you should take your business elsewhere. Heartland builds good coaches, and they like to build them the way the customer wants them if possible. As Jim said, sometimes that isn't possible, but no one knows for sure until you ask. Ask your dealer to check with the factory about anything you want. If the factory says it can't be done, then you either look for a different brand or live without it - your choice.
My two cents worth.