File a request at bugzilla.
https://bugzilla.redhat.com
You will have to create an account if you don't have one.
Choose Fedora
Choose a component, that is, something relating to the package you want to suggest.
I would use RFE as the subject. (Request For Enhancement)
Then describe the package, where its source is.
Unless you want to create the rpm yourself, in which case, I think it's pretty much the same, but you'd attach your rpm to it. (Might need a sponsor too, I don't remember.)