[jacquesm]

If you replace the Teensy 4.x it would have to be something very close to the same pinout, foot print, cost and features otherwise it would just be a new product. Ideally you would find a way to source the Teensy directly bypassing Sparkfun.

[ptorrone]

sparkfun is the single source supplier (and now maker of the product).

[jacquesm]

Yes, obviously, but they don't make the chips, so can't you just source the exact same chip, make thing pin compatible and call it a day? Then you'd have a drop in replacement, any changes you make will cause disruption for people downstream.

https://www.nxp.com/part/MIMXRT1062DVL6A

[15155]

Spinning an IMXRT1062/IMXRT1064 design sans the terrible Teensy bootloader should take a day or two at most.

These chips have perfectly-fine ROM USB bootloaders and SWD, don't ruin them by adding extra garbage.

[djmips]

The layout of the Teensy 4.x was challenging as I recall with the speeds involved. But maybe you are a demigod of compact high clock designs.

[15155]

Nothing on that board is remotely high speed or challenging.

USB HS on a board that small is a non issue: it's one measly differential pair with easy impedance requirements.

[djmips]

Go ahead and make one then, we'll be thankful.