> I *have to* maintain /etc/ethers, and I *have to* nail down some arp
> entries. Having to maintain two files with identical data doesn't interest
> me when there's a clean, good solution available that lets me use a
> single, already defined and populated file.  This is free functionality,
> essentially, and it solves a real-world problem for me.

May I suggest a different solution:  change the syntax of the file arp
reads, i.e.
hostname * [temp] [pub]
   will use /etc/ethers to lookup the ether address for `hostname' or even
hostname ethername [temp] [pub]
   will lookup `ethername' in /etc/ethers and use the ether address found
for `hostname'

This way you don't have to add to the /etc/ethers syntax, you have fine
grained control which entries from /etc/ethers get used and you don't add a
new meaning to /etc/ethers.  Adding a new meaning would indeed be a really
bad thing to do (cf /etc/shells).

    christian