I played with peer zoning a bit, but ran into a significant downside:
From the FOS Administrators guide (pp 356)
Peer Zones are configured and managed using zone commands with the
In the Peer Zone, devices must be identified as either WWN or D,I devices. Mixing WWN and D,I
device identification within a single Peer Zone is not allowed. Aliases are not supported as devices for
a Peer Zone.
If you have a large and complex environment, then aliases are pretty much essential to keeping things clear and readable. Maintaining peer zones, when they are just a pile of WWNs, is going to be a difficult, and error prone, undertaking.