With drones being so popular and TVC rockets starting to show up I think an Arduino designed to fly would be a good seller. The Nano BLE Sense is a decent fit, having an IMU and pressure sensor onboard, but I think we can do better. So far the best option I'm aware of is the Nano BLE Sense but I think we can do better. If someone makes a board with most of these features I would probably buy several of them:
Start with a board that has four good mounting holes. The MKR format would be a great fit for rockets. Alternately something with a 30x30mm mounting footprint would stack with existing quadcopter flight computers and PDBs. The Nano may be smaller but I ended up needing to solder it to a breadboard to use it which ended up taking more space than an MKR anyway.
High speed processor. Applications such as thrust-vectoring control and auto leveling require a quick response and lots of complex math. I would treat the BLE Sense's 64 MHz processor as a minimum and go up from there if possible.
IMU, specifically something like a BNO055. This particular model pairs the IMU with a separate processor to compute the absolute orientation. This would take some load off the main processor and lighten the code a bit to leave more room for PID controllers.
Pressure sensor. Turn it into an altimeter with a little bit of math. Some pressure sensors will compute the altitude for you, similar to how the BNO055 will compute orientation, though that might not be worth the trouble since altitude calculation is relatively simple compared to orientation.
High G accelerometer. I have yet to find an IMU that can record more than 16 Gs but if this board is going into a rocket then there's a good chance it will go well over that. The brute force approach would naturally be to include another accelerometer on top of the existing IMU (which I plan to do with the BLE Sense) but now the accelerometer is competing with pyro charge continuity checks and servo feedback on the analog ports.
Micro SD card. If you're going to use an Arduino in an aircraft chances are you'll want some data logging capability. Bonus points if the SD slot includes some sort of anti card drop mechanism so you don't lose the card and/or corrupt data when you inevitably crash the drone.