µcontroller choice

Hi all!

I've built a small serie of a devices using arduino nano, now I would like to make a large serie. But I'm strugguiling with the architecture, here what I need:
-Something faster than the nano
-I need BLE connectivity

Here are the option I'm thinking of:
1- RFDUINO: http://www.rfduino.com/
Pro: I can have an ARM M0 32bit + BLE for only 14usd for the SMT version, it's small and it's even compatible with my existing arduino sketch!
Cons: I will not be able to update the sketch over the air, and adding usb just for firmware update to my design seems complicated

2-designing the ARM M4 + cheap BLE board https://mchck.org
Pro: M4 + 50Mhz and a 5USD BOM,I can get inspriration from the great mchck.org project and just add one of this alibaba cheap serial to BLE board to my design around 5 usd
Cons: it's more work that opion 1 and risk, and at the end it's very close to the RFDUINO price

-Do you know if I could load a arduino sketch in an mchck.org like design using Teensyduino?
-Do you see any other option that I could be missing?