Someone on the forum did that a few years ago: removed the dinette to allow room for an enclosed head. It seemed kinda drastic to me. The head is the "room" in the boat where we spend the least amount of time in any given day... but, when you need a potty or want a shower, nothing else will do.
What would you give up to have an enclosed head/shower in a 22? Dinette? Galley? Both of those are very important to the way we use the boat. Put up walls and remove either the dinette or galley, and you have really changed the functionality of the 22. Bye-bye all around visibility in the cabin. No place to cook or eat? You have to be realistic: there is only so much square footage in a 22' boat.
We decided on a 25, not just for the enclosed head... the extra foot of beam is part of what makes it work: room for the water heater, fridge, and more storage. Room to pass each other in the aisle. The design of the 25, with covers for the windows in the head, allows you to have visibility and privacy.
Lots of people spend extended time cruising on a 22... with a porta-potty and sponge bathing. You just have to understand and accept what the space will allow. I would like to have an island bed, and room in the salon for a couch and a couple comfortable chairs... that's not going to happen in a 25' trailerable boat. So, we accept the dinette as our inside seating - one of the compromises we all make on a boat. For us, the 25 is the minimum we feel we can comfortably spend extended time on.
If you buy a boat that is a long ways away, you can always have it trucked/delivered to your destination... you don't have to buy a truck and trailer if they don't figure into the way you will actually use the boat. There is a reason, though, why most folks with a 25 DO have a trailer. I think it is one of the best features of the boat.
Decisions, decisions. I first started looking at C-Dorys, thinking the 22 would be adequate for us. No doubt we could have made it work, but our usage would have certainly been different... I don't see how we would be doing extended time on the boat - neither of us are enamored with schlepping our stuff to marina showers. Certainly, Bill & El did it for a decade; others are still doing it. Realistically, it isn't going to be for everyone; we all have different minimum requirements. I don't think I would be interested in renting a motel room for a night without a bathroom in it.
Good luck with the decisions. I am absolutely NOT trying to talk anyone out of a 22. Many people buy boats for the way they think they will use it... boats with two cabins because "family, friends, and neighbors will probably want to cruise with us." If having an enclosed head with a shower, more storage, hot & cold pressure water, a fridge, and some elbow room (don't discount "the shuffle" of getting around each other in the aisle) sound like what you'd need to be comfortable onboard, you might want to figure out a way to get a 25 instead of trying to redesign a 22.
Best wishes,
Jim B.