Tankless water heater upgrade

I don't really plan on doing any boondocking personally... So constant water shouldn't be a problem.. I really didn't picture "navy showers" in the rv. After tent camping all my life. I pictured long, hot, private showers in the rv. I just don't think I'm going to be happy with 6 gallons. I've already sank this much money into buying the thing. I might as well sink alittle more right off the bat for something i will greatly enjoy for as long I keep this. The interior is perfect. But I noticed in my dry run.. (driveway camping) after awhile the couch and dinette are just uncomfortable. So im thinking of gutting those and starting over anyways. Why not go the full mile for optimal performance. This is definitely happening. I just was curious, who else has done this and anything they can recommend. I'm not reinventing the wheel, I'm positive im not the only one who's thought about this. I should probably look at how the more expensive coaches did theirs, and what type they used. I would gladly pay more then a $1000 if i had to... but the units themselves aren't priced that bad. It's the install that's going to get me, I might need to pay someone. I've built airplanes my whole life tho, so it might be within my knowledge to figure out. Besides with the problem I originally had with the squirrel. I know how most of the wiring, ect is set up now. So im feeling more confident. *** adapt and overcome **