New customer specifies the country during registration, and after that, depending on the country he selected, he will be prompted to fill in specific set of custom attributes:
1) If country is Russia, then customer fills in ИНН, КПП, БИК, etc
2) If country corresponds to he "EU" tag, then VAT, IBAN and others are to be filled in.
It should be possible to add other attributes to the "attribute set" and configure validation rules for any of them.
The feature is intended to improve/replace "Country specific settings" functionality.
The feature has the ID PBA-62117.