Let me know if you were able to port your patch to the latest
jsonpickle, it sounds useful.
I managed to reimplement the dict_key object patch on a fork of http://github.com/davvid/jsonpickle
I haven't implemented it as an optional feature as it now uses a tag to flag a dict_key (so no messing with 'eval'). I don't think there is any performance or backwards incompatibility issues with this.
My patch covers any objects as dict keys - but the refs between keys and values don't work yet.
I've also taken out the test_broken_repr_dict_key test, I'm not sure what the intention of it was and if it still applies?