It is very easy to overload package versions locally for your needs, and it's quite easy to push that upstream to Guix so that others may benefit as well :)
[0] https://guix.gnu.org/manual/devel/en/html_node/Contributing....
[1] https://guix.gnu.org/manual/devel/en/html_node/Defining-Pack...
[2] https://guix.gnu.org/manual/devel/en/html_node/Defining-Pack...
[3] https://guix.gnu.org/manual/devel/en/html_node/Package-Trans...
The problem isn't contributions, it's reviews
I've noticed that I get fast merges if the package are popular