We just moved from ITG and have all of our Vendors created as Clients. Several of our Asset Types had fields that would link back to the Vendor/Client where more specific information could be found. For example in an Internet/WAN asset we had a field that would link to the Provider, where you could get more info on contacts, KBs, notes, etc.
When editing the asset layouts I'm not seeing a Client as an option in the Asset Link type.