Not to be cold, but realistic.....it sounds like you're having health issues that could easily cause you more serious problems in the not so distant future. Hopefully, you continue to improve, but I would make more simple plans.
What you're thinking about doing is going to take a lot of planning and modification to make it work. When done, you'll have something that has no value and will probably become a fight to get rid of. As others stated, if I were the park owner, I would say no. Even though it may look nice, they will know that if you up and leave they will be stuck with a hunk of junk.
I would look closely at your budget and future needs. The park model sounds like the way to go. No, or very few stairs, more room to move, especially if a wheel chair is needed. If your health changes, you'll have some value left if you can no longer use it. You could even think about renting it out if you need to.
Lastly, you have to keep in mind what will work for your wife, if she needs to step up and take more of a roll in your care or financial situation.