filename of custom themes has bad path

The filename of custom themes stored in system table has hardcoded paths. On multisite installations, they are something like sites/my.site1.com/themes/... The problem is that when renaming or moving sites this creates errors since the sitename is hardcoded rather than a parameter. Perhaps this is a feature request, but basically I just want theme_editor to support this piece of core functionality.

Thanks for a useful module!