It seems that many of the conversions are modular... and you could quite easily add what you need in the future.
If you were going with the GTRV pop top, you might consider having them include the fan and solar set up that I saw on their website. You would need to decide how much battery you need. When I had Waldoch do my Sienna conversion, I added two group 27s.
2019 Roadtrek Simplicity SRT (almost a Zion)
2015 Roadtrek 170
2011 LTV Libero
2004 GWV Classic Supreme