Hi,
Re. your first question (conversion routine) I would like to advice you as follows. All mentioned Characteristics already contain the conversion routine ALPHA. It means that during data staging the characteristic values are saved in internal format (i.e. with leading zeros). During reporting the conversion to external format (i.e.w/o leading zeros) automatically takes place. In my opinion you should not interfere anywhere in order to avoid any (e.g. referential integrity) problems. The output during reporting will be in external format (as per business requirement) so no need to do anything special.
Best regards,
Sander