@Putnam's answer is actually a bit understated, as functionality has been reshuffled so what used to be one key action can now be two or more mouse key actions, and some functionality that formerly resided in multiple keys now can be in a single mouse key action (but most often split into several, but along different lines).
Thus, it wouldn't just be the UI that would have to be duplicated, but the functionality underneath would have to be reverted as well for the old key binding scheme to work. That already exists, in the form of the pre premium versions, at the cost of no change to anything else either. That is, however, the best that can be offered with the old keybinding scheme.
Thus, there's no going back to the muscle memory keybindings. If keyboard support is restored (which is intended, eventually), and rebinding of keys is supported (which I hope, as that's generally a good thing, even though I'd probably rarely use it myself), the best you could do is a mashup between some things that use the old UI bindings and some that are using new ones (or ones made up by the re-binder). I think such an attempt would result in something rather bad, though, as the advantage of re-binding everything from scratch means bindings can be more logical than the result of decades of adding new keybindings to free keys as new functionality was introduced, so re-learning a new set with better bindings should be better in the long term than clinging to an increasingly weird mix of old and new.
Here's hoping there won't be too many more years before full keyboard support is restored.