You can script the process at each client but you will still have to do it per client since other factors will have to be considered; per client backup and recovery, per client audit related requirements, per client regression testing, per client downtime (unless patch be applied while DB is online), etc... if clients require support during update then turn-around time and other delays (scheduling) will also have to be considered. I doubt clients would appreciate you connecting to their databases remotely and doing an update without giving them chance first to do whatever they need to do at their end.

Alternative would be similar to patching and migration... patching would involve proving clients with scripts they can run (they can do their own backups before applying your patch)... for migration clients download new app and DB, then give them option to migrate data from old database when creating new DB. That way you can sync version control of front-end modules with their back-end counterparts since a break in backward compatibility is inevitable. Comparable would be Oracle technology (9i, 10g, 11g versions for front-end tech and DB)