I'll be blunt. I don't get this two-shift operation. I don't see myself ever using this feature of the WP43C, so no problem for me, but it causes some problems (on the calculator, maybe not the emulator):
It takes away assignable slots, two (or one, if we do as the WP43S does) labels from the [SIN] and [COS] keys + our yellow shift key and its two possible labels which are rendered obsolete.
That's 5 or 7 opportunities lost.
Plus it invalidates parts of the user interface, even requiring extra printing on the faceplate, with adds to the entropy there.
Plus it creates the need as you mention in your post to rearrange labels. In my mind, what we're changing was just about perfect.
If we could change faceplates (and keys) as we can on the emulator, I'd get it, but now I feel that we're compromising our way away from perfection.
The consequence is adding even more easter eggs, more things to remember, more to muscle memorize, more visual stuff to deal with on the faceplate. Three keys will have the wrong text printed on them, two of them the wrong labels above them, etc.
I am of course biased by having no need for that separate g shift key at all, but any gain comes at a significantly higher cost - in my personal view.
Do we really want to go there?
PS: As I was typing this on my iPad, I got conscious of how to activate CAPS LOCK on the on-screen keyboard. Guess what - double press the shift key (albeit within a time limit). It's not just us...