Vetting of user registration

Because the site is to be trade only supply, the client wants to vet the registration of new users before allowing full access to the site to view product prices (which are now hidden until logged in).

Been looking at an old thread on double opt-in showthread.php?t=14143 but this doesnt seem to be exactly what the client is asking for.

I have previously successfully added company name and an extra address line to the registration page and under-estimated the time it took to complete this exercise because it involved changes to update, confirm, checkout and all the backend pages for the orders and user tables.

Therefore I would welcome your comments and if feasable a breakdown of what would be required for implementing the vetting system described above.