Honestly I think it would be a good ide to remake the PV*SOL program. New Engine, HUD and interface.
Maybe it could also be an idea to go into a cooperation with a CAD software maker to integrate there drawing engine/tool into PVSOL. Maybe something like SketchUP because it's fairly easy.
Also large project takes a fair amount of ressources when calculating and it's nonsense that the program do not utilize more that one CPU core.
I use PV*SOL Premium for my everyday job.
I have a profession degree in CAD, 3D drawing and product/process optimization, and I really think this would take PV*SOL to a entirely new height.
The calculations and options in the program is great, so I think you have something really good. It just seems outdated.