Hmm. I just bought a new 36 month battery for $110. Never in the last three years did I have any issues with the battery not being "preserved." $2000 of solar for no measurable impact on the usability of my ICE? This doesn't make sense. $2000 buys me 50 years worth of 36 month batteries. The only time you would need trickle charge is if the car is parked for long periods of time with no plug-in available for trickle charging. That's a niche need. Plug-in trickle charge for the life of the car would cost a lot less than $2000.
RV? When parked with no plug-in power available, sure it would be nice to have some electricity without having to run the motor. Other than that, the tiny bit of solar you could put on the roof is completely insignificant with respect to the power needed to move the extremely heavy RV.