I encountered several similar polite refusals to install owner-furnished items while planning my build.
ETI's "Built for You" slogan has some tremendous options and IMO is a bona-fide claim relative to most other RV manufacturers, but they will be the first to admit they aren't in the business of building truly 'bespoke' trailers. That's perfectly understandable IMO, no worries!
IMO it's always best to ask ETI about your specific situation
without any reservation (i.e. don't 'filter' your 'asks' based on what you read on this forum) and see what they will and won't do in your specific case - it never hurts to ask and
the answer is subject to be different from past responses at any moment in time. Sometimes the answer may be different due to specific combinations of things in-play for a specific case.
Bottom line, you'll never know what is possible (or not) if you don't ask the company that can make it happen (ETI) and there's no reason to not at least ask for everything you might wish to have.
Have Fun!