Hello,
Funny you should mention that
The timing of your question happens coincide with the near completion of this exact major new feature.
It's already available in it's 90% complete form with the pre-release binaries:
https://www.directadmin.com/clients
view your license, follow the pre-release install instructions.
The only bits that are missing (as of May 24th) are the extra IPs for domain pointers, and for the ftp setup (this gets messy for owned IPs).
This feature not only supports multiple IPs per User, but also multiple IPs per domain. This allows for IPv4 and IPv6 IPs on a single domain.
The related feature is here:
http://www.directadmin.com/features.php?id=1080
With the pre-release binaries, you can test drive it right now.
Related pages in the skins:
Reseller Level -> List Users -> user -> Modify User -> Additional IPs table
User Level -> Domain Setup -> domain.com -> Addtional IPs table
Note that the Additional IPs table will only show up if the User has multiple IPs to chose from. If he's only been assigned 1 IP, then the table will be hidden.
As with all major new feature, we'll be leaving it in the pre-release form for a while (starting once it's done) so it can get some solid testing under it's belt. As mentioned, it's not 100% done yet, and I have not yet tested it a whole lot so there may be bugs.
John