Problem: In Guix, a makeinfo running in build phases cannot generate epub3?

Sent this to Help-Guix Info Page, but I don’t see it published, so I’ll also post it here, with mild editing, because I can’t help myself from pointlessly fussing over minor phrasing improvements.

Hello,

I am writing package definitions for the Texinfo version of the R7RS-Small standard document. Each package would create a different file format, so the packages will be named:

r7rs-small-info, r7rs-small-pdf, r7rs-small-epub, etc.

I am having a problem generating the epub version because the native-input texinfo
package, the one responsible for compiling from the Texinfo source, does not accept the --epub3 (or --epub) flag. I have
tried adding the perl-archive-zip package, but that did not
work.

Also, if you have any criticism regarding the structure of the package
definition and the (lack of?) wisdom in defining different packages
using a single procedure, please provide them.

Thank you!