Should support having commits in a thread float on lower thread's commits - perhaps by rebasing

I would like a more quilt-like work flow by being able to easily rebase higher threads on commits made to lower threads. I'll quote from IRC:

11:12 < fbond> Hi, I'm using the loom plugin. When I make changes to a thread and then move up-thread, the new changes to the lower thread are applied as new commits on the higher thread, but what I really want is to rebase the higher thread on top of the new commits on the lower thread. Anyone follow me?
11:12 < fbond> What is the best way to do this?
11:14 < james_w> fbond: you may be able to do it with the rebase plugin.
11:14 < james_w> I'm interested in why you are using the loom plugin if you want to do this though.
11:15 < james_w> rebasing a thread will probably stop you from moving up thread from the one you rebase.
11:16 < fbond> Well, I want the loom plugin to act more like quilt, I guess.
11:16 < fbond> james_w: perhaps I should not be using loom, but should instead just branch and rebase?
11:16 < fbond> i.e. create feature branches...
11:17 < james_w> that would be the better solution currently.
11:17 < james_w> it may be possible to make a quilt mode for loom at some point.
11:18 < james_w> can I ask why you don't just use quilt on top of bzr?
11:18 < james_w> I'm unsure of what the tradeoffs here.
11:18 < fbond> Hmm... I don't really love quilt...
11:18 < fbond> I actually just used shelve for a while.
11:18 < fbond> But shelve is un-fun in that it doesn't deal with adds, moves, etc...
11:19 < fbond> quilt would be roughly the same in that respsect...
11:19 < james_w> yeah, shelves not viable for all this.
11:19 < james_w> true.
11:19 < fbond> The ideal situation would be an extension of loom that rebases when I do up-thread, I think.
11:19 < fbond> Maybe bzr up-thread --rebase
11:20 < fbond> Or bzr rebase --replace, to replace a section of history with another section...
11:20 < james_w> yeah, it's not ideal because it means that the threads above no longer share history with those below
11:21 < fbond> Well, they all have to be rebased...
11:21 < james_w> and lack of history means merging can't be as good.
11:21 < fbond> So maybe, then, `bzr rebase-threads' to rebase all threads above the current one.