While waiting for my parts to arrive I've been designing my layout and thinking about some custom firmware options that I think would be cool, thoughts comments encouraged!
Some of these are good reasons why using the Massdrop configuration utility is limiting, what I'm currently thinking:
Make the shift keys into
dead keys in addition to modifiers, once you get above 100 WPM using a modifier becomes unreliable and uncomfortable, would be much easier to just tap shift knowing that the next character would become upper case.
Make right alt, left alt, right ctrl and left ctrl available as
dead keys in addition to modifiers, if no other key is pressed between down state and up state we can assume they are being used as dead keys instead of modifiers and we can assign a new role (I'm thinking
Diacritics for foreign languages but it could be anything that a
dead key is useful for.
Put the teensy in the left panel, enable one handed keyboard with mouse. The biggest trouble I find with one handed typing is that some sort of modifier is needed to "flip" between the "right" and "left layouts and it's really hard to use your left hand to do this since you need to be able to type normally with all fingers.
Ideally I would use an extra button on my mouse to switch, now we need a way for the mouse to communicate with the teensy/Ergodox to tell it to "flip sides". As far as I know the only signals that could be used to signal something like this to the teensy are the "Lock keys", and fortunately one of them is largely unused; Scroll Lock.
It should be possible to modify the firmware to enable it to use "Scroll Lock" as a programmable input, from that point it's easy to program a mouse to turn scroll lock on/off with a button.