Unfortunately, eSATA is a badly defined and followed specification, so supporting it directly may never be possble, at least for many of the older and cheaper designs that are in regular use, though it has been investigated.
For that reason among others, the ability to backup to a Windows Share was included in WLOC 2.0. Originally, this required that the PC be setup as a Hub, but was supposed to also work for any OneCare PC in the final release. I haven't attempted this myself, so perhaps you can give it a try and let us know how it works for you?
Simply create a share, then use the Network Location option in backup to select that share as the backup target.
OneCareBear