Last things first: having another layer before LaTeX -> PDF would - in my eyes - not make LaTeX any better but increase the bloat. But this is just a spontaneous opinion.
About PDFlib I'd just like to add that a commercial (non-OSS) product with a lot of language bindings is hardly a solution for a problem which obviously should be solved using a domain specific language.
We are currently still using LaTeX but are always looking to migrate to something else. HTML is our favorite but not the winner.
But, I'd still like to hear more about how you use LaTeX in your solution.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.