FWIW, the idea did have some merit and I appreciate your submitting it.

The issues are that the net gain likely isn't worth the API complication, that it opens a can worms (about manipulating the cache contents beyond load and store), and that it is at odds with the core notion of being transparent.

FWIW, the C version of OrderedDict now makes it trivially easy to roll your own highly performant variants of the LRU cache.