Hi Brandon
The Bullet 2 (like the original MP1) uses the older AR25 chip set while the Bullet M2 uses the AR71 chipset so the firmware is not interchangeable.
Because the AR25 based devices have been discontinued, we have not produced recent firmware for them.
That said, if you can load a generic version of OpenWrt on the device, then you can manually install additional packages (eg batman-adv) and the SECN scripts. But it will entail a bit of work.
OpenWrt firmware for the older AR devices is available on the OpenWrt Downloads web site.
Up to version BB the firmware is in a directory called "atheros" and from CC on it is in a directory called "ath25"
Be aware that the flashing process is also different and you may have to use tftp as per this article:
Regards
Terry