Anything is doable, given time and/or money, but I think making a wider door would be a tough one -- because you'd have to re-do so many things.
1) Metal step unit, which may be integrated with hitch and/or bumper (Atlas Metal Mfg.)
2) Molded fiberglass "hood" over exterior of door (because rear of coach slants inward, molded section is specially molded to be plumb for door)
3) Well, this one may not apply to you (
), but the shower and closet (and refrigerator) limit the effectiveness of a wider door once you get inside).
On the other hand, I found a couple of other mods that really reduced the narrow feel, at least for me (because I disliked it immensely).
1) On the outside, I moved the spare tire to the front onto a front hitch mount. Ahhhhh, elbow room at the door (plus less weight on the close-to-limits rear axle, and more weight on the has-spare-capacity front axle).
2) On the inside, I remove the Very Large Refrigerator, which protruded into the already narrow aisle. The new compressor refrigerator I installed sits back something like 3-4", which makes a big difference.
2a) I used a refrigerator that has a 46" high counter over it, for additional elbow and visual room, but there is a "next model up" refrigerator that would be closer to the original size/height, yet still less deep.
2c) I eliminated the little cabinet under the refrigerator (which would have been shallower with my new refrigerator anyway), and instead re-insulated the gen box to be quieter/cooler/less bulky, and the refrigerator thus cantilevers over that area by about 4". More visual space plus a place for shoes, that bag you need to take out to the car, etc. without tripping over them.
3) On my rig, the face of the closet ran a little crooked. At the rear door, it attaches to an angle iron that is part of the rear shell. But then as it came forward to meet the refrigerator wall, it also came outward into the hallway slightly. I re-did that to be "straight," which gives another inch or so in the hallway, but is not noticeable in the closet.
4) This is a bit more tangential, but still has some effect: I removed the giant/square microwave cabinet from over the stove. No more limbo cooking, plus much more visual space (I made that cabinet in line with the cabinets over the dinette area instead. I don't want a microwave, but some Chinook's had them under the stove top if they did not have an oven).
I realize some of this may not apply to you, since your rig doesn't have a lot of the stock cabinetry left, but I figured it might still be somewhat helpful, and plus of course others reading might find it of use.
BTW, I don't mean to be discouraging on the door - heck, I mulled over adding a side door before deciding that even I have my limits
