Comment 4 for bug 351473

I gave some brief implementation advice in bug 1262824, but it would be more useful reproduced here rather than in a duplicate bug:

Yes, the underlying resize_use_free implementation in partman-auto has only ever supported selecting a single disk. To fix this, it would be necessary to refactor it to work something like some_device (so the choices script would only check that it can work at all, while the do_option script would offer a selection of the relevant disks), and then ensure that ubiquity still works with the amended flow.