I'm giving this a try now, I'm a blender user as well and own a license of PlayUp. My model is 180MB, pretty tightly optimized except for containing a demo layer since it is a renovation.
The online converted processed the model in about 8 minutes and sent me back a Zip file that unpacked to 324MB. Opened in Unreal 4.16.2 It gave me the project the name GeneratedProject, it would be better if it used the original file name. It also didn't respect the layer state and included the hidden demo layer, it would be better if it excluded geometry hidden in the last saved view in my opinion. Some textures came in scaled to something below 10% of what is in the model. Shadows are working well.
15 minutes in, the model already looks better than it would have after a couple hours of conversion and file wrangling in either PlayUp or Blender.
Went to build the model and got 4,434 lighting errors, both Object UVs and Lightmap UVs are overlapping. I don't recall the exact error but I usually get a more serious error than this from PlayUp. I see that you are also looking to sell model "enriching". I would suggest texture work as a more useful and marketable service since unlike populating the model, which could be done by anyone, you would be selling the knowledge of quick fixes caused by your own conversion process, it would also be easy to build a library of textures since sketchup users are typically fairly restrained. Indeed, a good freemium model might be to charge for the photo texture conversion but provide properly named and scaled blank textures so that the free output is essentially a beautiful clay model. I'd love for yal to monetize this so that you can put serious development time into it. It's clear that whatever secret sauce you're cooking the conversion with is far tastier than the PlayUp team's.