What I have in mind is an ability to parametrize the transcoders like
the following:
(org-export-define-backend 'html
'((paragraph . ((paragraph-is-a-link? figure-transcoder :name figure)
(:unless 'figure paragraph-transcoder))))
:transcoder-conditions
'((paragraph . ((paragraph-is-a-link? (lambda (paragraph contents
info)...))))))
Several ideas in the above:
1. Name features as "transcoder conditions"
2. The transcoder conditions are now linked to specific Org AST element.
They may not only be matched against the whole parse tree + whole raw
Org text, but also against the specific branch of AST + chunk of raw
Org text corresponding to the branch + the actual exported contents
of the AST children.
3. "feature implementations" are no longer needed. Instead, export
transcoders can contain the implementation lists inline. Each
implementation is selected not only depending on the presence of the
"feature"/transcoder condition, but also depending on multiple
features or arbitrary lisp expression results.
4. :when/:prevents apply to specific (possibly named) implementations.
This makes more sense than matching against feature.
For example, presence of svg images in latex export may or may not
mean that \usepackage{svg} is being used, depending on svg
implementation. We want to match against \usepackage{svg}
specifically rather than only against the presence of svg images.