I know you must have done that a while back, but out of curiosity, what did you replace it with?
Tried a few but settled on Less is More 6.4
build done by a 3rd party is on the way, if I didn't want a working compass then I'd give the Alpha a try.
XIAOMI have said Android 6 was coming to the RN2 but who knows when that will be, the MIUI developers are slowly working through the models. If they didn't spend so much time trying to irreversibly intertwine their apps into the OS it would have been here sooner ... then again MTK aren't known for speedy releases of kernal source code which is why a phone with a Qualcomm CPU is better.
Still, an official release of Android 6 based MIUI would allow an alternative to be created that much easier since they can just grab the hardware drivers to incorporate rather than source from other similar specced phones where manufacturers have been a little more pro-active.
If you want to see what it takes to remove the "XIAOMI Ecosphere" from an RN2 and tweak battery life, etc, see here
. I did it but didn't like the result, (a couple of annoyingly obvious bugs), so I switched ROM.
Think I'll save my pennies for the RN3 SE (kate)
, since I travel overseas it'd be pretty close to the perfect phone at a good price point, (if only it had NFC also).