Dealing with this as a deployment issue would probably be the best approach. Create a process or an application that will apply changes across all of the databases. Once approach to this may be to create a single database with just your stored procedures in it and a process that replicates all of the procedures to your other databases when a ddl event fires. This could be managed pretty easily through triggers or even SQL replication and would ensure nothing ended up out of sync.

Regardless of how you do this, I would try to establish this type of infrastructure right away and make sure everyone sticks to it.