Let's say 3 development teams (1 at customer's site, and 2 consultants) with no LAN or VPN to join them, only mail or ftp. Each team owns licences for SF and DDT, and can create deployment packages to apply on customer's SQL Servers (and of course on SQL Servers for tests at consultant's office)

When I receive customer's package, I can import it in a profile and deploy it from that profile. From another profile, I generate a package, and customer may deploy this package I'll send him. And of course, each deployment delete and  replace what was locally written

How could I merge the 2 packages into a single, in order to see all modifications in a single profile? from within DDT? with a merge replication in SQL Server? with a versionning product (Visual SourceSafe or another one)?

Thanks in advance for all advice.

Is this for two seperate applications? Or do you have multiple teams working on the same application / database? If the former, than seperating them logically by team into seperate profiles and DBs would be the best bet. If the latter, than some parity will need to be kept to prevent overwriting (possibly seperate profiles, with apporoved changes being brought into the "production" profile?)