Using Craig's latest audit script, I found a couple of remaining cases of map:new:

>>>  Replace the following instances of the function map:new with map:merge.

./transform/beamer-epub.xql:32         map:new(($options,
./transform/beamer-web.xql:30         map:new(($options,
./transform/beamer-latex.xql:34         map:new(($options,
./transform/beamer-print.xql:32         map:new(($options,

I've submitted a PR with a fix: !64 (merged).