I am very much not a uscan expert, but the attached watch file appears to do
what you want.
Key changes are:
1. Adding a dversionmangle line to each entry that modifies the Debian version
number to extract the information that should be used for each upstream
tarball. Your case is a little interesting because one of the tarballs has a
different numbering scheme.
2. Change the version entries to remove `group` and use `ignore` on the last
entry.
3. Add `uupdate` as the script at the end of the file.
There are probably many other ways you could accomplish this.