[This issue concerns redhat-rpm-config as well.] Every now and then, there's a need to build packages that mangle the resulting binary package name from a single unchanged source package, based on some build time conditions. Let's assume package (SRPM) foo. Based on some options, the binary rpm built from it can result in foo-bar or foo-quux being output. But the debuginfo package will always be named foo-debuginfo, making it impossible to store the debuginfo packages resulting from foo-bar and foo-quux in the same directory/repository/whatever (since they're always the same, foo-debuginfo instead of foo-bar-debuginfo and foo-quux-debuginfo). Making the name of the debuginfo package customizable would help, for example by defining this in foo.spec: %define debuginfo_name %{name}-bar-debuginfo ...could result in the debuginfo package "foo-bar-debuginfo".
Rather than customize a rather arcane and fragile mechanism further with Yet More Parameters, I'd rather see an explicit subpackage used in spec files. That's all a -debuginfo package is. See glibc for how to generate -debuginfo as an explicit sub-package.