How can I fix Droid2 "Link Contacts" so it chooses the right primary name?
The Droid2 has a protected bootloader, meaning custom ROMs can't be loaded unless it is cracked.  (It hasn't been cracked yet).

That said, you can root the phone and you might be able to replace the Contacts app with another one.  The problem is that the Contacts.apk file is more than just Contacts -- it's also the Dialer.  Kind of an important file.  Replacing should be OK though as long as you back up the original and can restore it, but don't expect the replacement to work.

Googling "2.2 contacts.apk" should give you a few different versions of the app that you can download and test out.  Note you probably need to deodex your phone before you can replace a system app.  To actually replace it, use an app like Root Explorer to browse to /system/app, mount that folder as R/W, rename Contacts.apk to Contacts.backup or something, and copy in the new Contacts.apk.