Welcome,
I might be able to help guild you a little.
The 2015+ Models all have 15” wheels so the wheel upgrade is not required.
As far as a lift goes, “I” think they are not required but are beneficial. We used our 23D for 2 years without a lift and then I decided to build a custom lift kit. Link here
http://www.airforums.com/forums/blog...lift-kit-2901/
Since then I have lifted 4 other Airstreams. So I am quite familiar with them.
The 3” Lift has no noticeable side effects in towing or otherwise.
It does give you piece of mind when entering and exiting gas stations, camp sites ect. The increased ground clearance helps with gravity when dumping tanks.
Sewer connection clearance goes from 9” to 12”.
Anywho, a lift is NOT needed to safely use the trailer. I can only think of one instance where I was close on rear end clearance and that was a place I did not need to be anyway. Now that I have the lift we just tow it anywhere.
Also. IF you have a taller tow vehicle the lift help with the amount of drop you will need at the hitch.
Hope this helps....