X18D is a nice little [Note: Little] hybrid. Remember the old saying about trying to load 10lbs of "stuff" in a 5 lb bag. Adding an outlet here or there could be pretty straight forward DIY project if you're at all handy. Additional seating??? Remember you have a 5 lb bag. Mod to shower? Assume you can do it if its the same footprint as the shower, but what do you plan on doing with the "small" tub? Going to a dealer for any of this will likely cost you a bunch. Dealers love to do mods and charge outrageous labor rates.
When we go our WH last year, we did some mods but many of them involved taking stuff out. We removed one of the 2 lounge chairs and 2 of the 4 dining table chairs. Only 2 of use and we didn't need the extras. Added stacked plastic totes to the shower since we rarely use it for showers. When we do the totes are easily moved to the bedroom. Added battery powered wireless wall switches to turn on lites in the main area and bedroom so you don't have to reach up to a ceiling light when entering at nite. Several more but we always considered the need / function before deciding to do anything.
Not that familiar with your model, but a small hybrid can be a great camper for a small family or couple. When you add too much stuff and load it up with personal items and family, it can get real small real quick.
Suggest you do some camping and take the opportunity to see what others have done with similar sized units before you pop for your own mods. Unless you have an unlimited budget, consider what you can do yourself. There are a lot of Utube videos showing you how to do a lot of them.
