You don't have to grant each procedure separately, you can grant execute on the schema (or for the entire db, no matter what the schema, if you prefer). The user then automatically can execute new procs as well, without another command being issued.

One really big issue with db_owner is that it can DROP the database! If you get a hack or some bad in there, are you really ready for that to happen?!

The apps that require db_owner are, frankly, poorly designed. Yes, the app may even need db_securityadmin (so that all access can be administered through the app), but it never should require db_owner.