Why do you think that telling me I'm not sensible for doing books that interest me will convince me to do books you think I should do?
The problem is not that you want to do the books you want to do. The problem is in insisting that there HAS to be a "one size fits all" solution which is sufficiently complicated to handle even the most complicated book. A different "solution" would be to come up with a relatively simple solution which fits well 90% of the books which PG has historically published -- which are relatively simple -- and then the people who want to do the really complicated stuff can still use the techniques THEY want to use to do the really complicated stuff. We already have TeX and PDF to handle really complicated books, and those are pretty good solutions for really complicated books, for example. Or if you want to create a TEI system to do those books, go for it and good luck. Or use PDF/A "Over" for example. But don't insist that WE all have to buy into YOUR complexification that YOU want to use in YOUR efforts just because YOU want to do YOUR really complex stuff! Again, most PG books are pretty simple. And guess what, PG is *still* doing quite simple books quite badly. HTML on desktops works pretty well. Everywhere else is quite broken.