Hello Tim,
We already do most of what you stated above (composing XML document) but we use TeX as a typesetting engine to produce PDF files,
The problem with TeX is the time waste in manual layout,we want to exchange TeX with APP since APP provide friendly UI, and more automation than TeX,
We tried other typesetting engines, but most of them fail due the heavy tables (table groups,long tables and landscape),figure groups(14 sub figure), Math equations ( 60 displayed equations on Average per article) we deal with in daily biases, how does APP handle this staff ?