Here’s my list.
A Framework released placeholder expansion card, so you can essentially cover USB-C ports you don’t need or aren’t using with nothing.
A touch screen.
An input cover with no touchpad and the keyboard nearer to the front edge, or the touchpad above the keyboard on the input cover.
A chassis allowing for an easy exchange/removal of the top cover where the display and webcam are located for an easy exchange, or use with a dock for Desktop applications.
Easier battery removal/exchange, such as allowing for a hot swappable battery. This would probably necessitate a different chassis as well.
Side pointing speakers rather than down firing ones.
Wider stereo field on the microphones that are built into the webcam module.
A different bottom peace on the bezzle, so if you close the lid of your laptop, airflow from the fans can escape out the back more easily and keep the system cooler.
Better grip on the feet that keep the chassis raised up, or even exchangeable feet for the chassis.
A no fingerprint sensor option for the input cover, a no webcam option for the top cover. Both of these could be configurable at purchase options.
A power input only expansion card for USB-C. There have been and can be some problems when power can go both ways, such as with power banks that can provide and receive a charge over a USB-C port.
Beeps for error codes, at least some of them, in addition to or replacement for the lights.
Not specifically for the full FW13 itself, but part of it: A framework built chassis for the Mainboard when you choose to upgrade the Mainboard and need a place for the old one. The Coolermaster one is nice, but has had and possibly does have its problems.
That’s all I can think of for now.