* installing by just copying python files to /usr/share/themole is far from elegant.
Uh? This is the idiomatic way to install Python applications.
there is no byte-compilation of files, unless themole gets invoked by root (which in term is a bad thing itself as /usr/share gets written to at run time, and it is not cleaned up on uninstall).a simple --with python3 after "dh $@" won't do by itself either.
Yes, it would. dh_python3 does care of bytecompiling stuff in /usr/share/$packagename/ (even though it's not documented, sigh).
-- Jakub Wilk