Well, theoretically, I guess one could build the new module and include it in a new .trx, but you are right in saying that one should have a certain amt of trepidation in regard to flashing that to a router…
Probably the safest way would be to :
cd to the kernel source (I don't know if you used 2.4 or 2.6 kernel - there is a big difference)
do something like
make menuconfig ARCH=mips
and then the kernel config menu (in blue & white text) would come up…
go into the sections you need and turn on the bluetooth pieces you need as MODULES, save your config to whatever name config the toolchain uses
then build it (make all ?) it's beenawhile, you'd be able to find the modules in question in the kernel source dir
One could also do the menuconfig, but then use the toolchain to build the whole image .trx again… but just look at the rootfs dir , in /lib/modules/18.104.22.168 (or whatever)/kernel/drivers/bluetooth/
A key thing here is that when you alter the kernel config, the changes you make should be minimal, and only for Bluetooth. The less you change on a kernel config, the better, generally, and the more likely it is to work. It is possible that there is some structure needed for bluetooth _in_kernel_ , besides the bluetooth modules, and that this may not work.
Again, I'd be very careful (read: hesitant) to flash your .trx to your router.