@Simon
Don’t worry. You did the most work for html export and your work looks great!
IMHO anyway I would not have the expectation to let it look exactly as desktop version.
More I think it should be as simple as possible but should contain all informations in a transparent way for user.
If html structure is simple then anyway it’s no problem to use it for a future import again.
Based on your work and your css I did an example html file and was impressed how good you meet the desktop look and feel 
Within next week hopefully I will get the time to start including the export into my fork 
But for extending ffi definitely I need some assistance how to do that.
My plan is
- get it run by core
- define and include an ffi interface
- add a ui control(s)