here is the use case:
CPSDefault (like CMFDefault) requires cookie crumbler as a mandatory tool, this makes it impossible by using extension profiles to install other types of authentication tools (SecureAuth?, CPSKrb5Auth) that need to remove 'cookie_authentication' .
creating a base profile only to replace the cookie crumbler would involve an unnecessary duplication of the default cps profile.
basically, the cookie crumbler setup should be moved to an extension profile of CPSDefault, but since there must be at least one type of persistent authentication method in CPS (cookie crumbler, secureauth, cpskrb5auth, CPSUserFolder with PAS, ...), the selection of one of these methods must be mandatory.
so as an enhancement it should be possible to specify a setup step as mandatory among a list of steps that all perform the same type of configuration (e.g. "setting up authentication").
