Hey @RemovedIntent,
- HID/Rubberducky is possible but not planned at this present time.
- Yes to full Yubikey / FIDO2 support
- Battery is for two reasons: 1) We are pursuing a water resistance certification, so need to use some semi-permanent gasketing, and 2) Size. This is how you achieve smaller form factor devices with tighter tolerances.
However we have already discussed a DIY replacement kit being available in the future. Due to the device design, the task of replacement will be much easier than a modern smart phone.