> Do I have to make each RS6000 an ADSM server?

From the way you've explained it I would think so.  Since you have claimed
that your network cannot handle it, you need a way of doing your daily
backups.

> Can I make the remote RS6000 a client and backup to a remote tape drive?

Yes, but if you have network issues????  If your network cannot handle this,
then it cannot work.

> Can I make my remote drives another stgpool that migrates to our Omaha
> installation and adjust highmig to cause migration after the tape arrives
> here?

The key here is understanding your environment. You have 3 remotes needing
backups and the network seems incapable of handling them.  In order to get
the backups done, it appears you'll need to setup those remote RS6000's as
ADSM Servers.  Now once your backups are done, you have a multitude of
options for bringing things to the central site...

1) Migration - Using network resources.
2) EXPORT/IMPORT SERVER commands - Requires shipping tapes in most cases.
3) You could use Copy STGPOOLS but that's a bit tricky.

ADSML