Build of a custom registration module for DotNetNuke

I need a custom (registration) module for Dotnetnuke (6.X ->) (In fact a copy of the DNN registration module ...) This module needs to check if a) a user who wants to be registered allready exists in an external database (Sql server) eg. by checking email - address and Social Security Number and .... b) if these data exists the user has to enter a proposed userid and proposed password c) proposed userid must be globally unique d) proposed password must confirm to the rules as laid down in the [login to view URL] of DNN e) if entered data do not confirm this rule an error message is shown. The user may enter data again. f) if entered data do confirm to this rule the data are stored in the external database. The password is stored in the format which is determined during setup. Setup:- a) the database connection string must be entered in the setup of the module b) password format; hashed/text/ Normal DNN standards for setup of the module etc. are applicable. If the registration module of DNN cannot be bypassed the it is acceptable to suggest a DNN core change. To be noticed: This module replaces the DotNukeRegistration module. Advices for other functionality; welcome!