How can we improve WHMCS?

We are having huge problems because WHMCS doesn't include a field for the VAT/Tax ID. This is mandatory in all the Euro zone.

The workaround is to use a custom field, but this has a lot of drawbacks.

-WHMCS contacts can't have custom fields. Invoices using WHMCS contacts are wrong. Wrong=illegal.
-Domain contacts don't have it either (it's required for .es domains, for instance).
-A lot of manual intervention is necessary for it to appear in invoices, etc.
-Custom fields can't be locked, so customers can change this field and ruin the invoices.I think this needs to be considered an integral part of WHMCS user profiles, including a migration script for everyone that has been using a custom contact. Whenever a contact appears in WHMCS, be it a customer, a "contact", or a domain contact, we need to have this field.It's even more important than the phone number.This should be a real field, just like "Address 2" is (which is a hardly used field, IMO, but featured all accross WHMCS).The VAT# field should appear everywhere:-Client Profile Summary page, under "Clients information"-WHMCS Contacts-Whois contacts, when necessary (.es, I think .eu as well)-Invoices-Reports-Search-Field options (so we can make it required, not-modifiable, etc.)It's a very real need for any business in the Euro zone.