Rebase & submodules

So I often will have a submodule that points to one of my own forks, because I will have work done on a feature branch that hasn't been merged upstream yet. Assuming this merge takes a long time to get approved, I will occasionally rebase my topic branch to keep things up to date and clean.

However, any previous commits in my parent repository that refer to a SHA1 prior to the rebase will now be pointing to dangling/orphaned commits, which means I wouldn't be able to go back to that commit in history and do `git submodule update` since that checkout will fail.

One obvious solution to this is: Don't rebase. But, this could result in a lot of merging between the upstream and my fork which would make things not only ugly, but prevent me from making a pull request that makes sense to the upstream repository (They'd likely request a rebase in order to accept the PR, which I wouldn't be able to do for the reasons outlined above).

Are there any other workflows that would support this kind of model better?