I agree with those who suggest getting out and spending some time in your Airstream before upgrading much of anything.
You may find that what you think you want and need now is different from what you think you want and need 6 months to a year from now.
If you are not looking to boondock for extended
periods, what you have in place now may be enough to meet your needs.
We/I always took the approach of working with what we had in place in the Interstate, and haven't upgraded anything in 9 years of ownership and over 170,000 miles....replaced batteries and tires, of course, but no "upgrades".
Because we have an onboard generator, it seemed duplicative and an unnecessary expense in the beginning to add solar panels...and we never felt since that these were "required". Phones and IPads stay plenty charged with what we have.
I had a little plaque once upon a time that said "Happiness is Wanting What You Have, not Having What You Want".
I believed in that, it helped my mindset back when retirement and traveling the country couldn't have been more a pipe dream....and I still basically do.
Take some time, get a feel for your Airstream's limitations, and go from there, is my thought.
I basically disagree with the approach some have...and can afford...that everything must be 18K quality. No offense meant, just a different way of looking at it.
If there is something you really need
, you're going to know that.
You have a brand new trailer. Use the money you would spend on upgrades to travel.