There are a lot of people using a SketchUp to Photoshop work flow quite well. Liam’s work is a good example. (See his gallery thread here.) Using Leonardo in place of PS doesn’t matter, it’s the same process if you’re trying to get to those painting tools for final results.
I have, at least with Match Photo, inadvertently run into limits with SU on image resolution size; the native 24 mp images from my Nikon D7100 were too high for SU to cope with and caused bugs. I wouldn’t be surprised if you could hit frustrations trying to work with high resolution images the way you want.