Leo,
You can actually get 54 keys on a 7965 with 2 expansion modules (assuming you count the main station keys). Of course that doesn't meet your need. If you stick with the concept of using line appearances on a station to manage your 60+ user deployment then you may need to look at the expansion module for the 8900/9900 series phones. This means you would need a new phone to replace the 7965 and that isn't cheap.
If you used a 9951 or 9971 with the expansion module then you should be able to cover your need. See data sheet here:
http://www.cisco.com/en/US/partner/prod/collateral/voicesw/ps6788/phones/ps10655/ps10676/data_sheet_c78-565427.html
The module has 18 physical buttons with two logical pages. Therefore, each expansion module offers 36 individual appearances. The 9951 supports two such modules (72 appearances) and the 9971 supports three modules (108 appearances).
It going this route is inadequate, then you could look at one of the Cisco Unified Attendant consoles (http://www.cisco.com/en/US/partner/products/ps7282/index.html). I haven't worked with these applications enough to provide any specific guidance.
If neither of these options satisfy your needs then we would need more information about the requirements to provide more specific guidance. My inference from your post leads me to believe that the two options mentioned above are the most viable.
HTH.
Regards,
Bill
