Very good initiative! Signed.
Could you elaborate what it would mean for development of Mi Mix 2 ROMs, kernels etc in OP? You'll get more people to sign it that way.
Project treble will provide fast updates via Google because the changes made from vendor are separated and applied over the running OS in a way with kinda 2 different partitions
In theory xiaomi could give the sources for that and now everyone can compile stock Android os and flip the part of vendor they want to.
So yeah it could increase the availability of custom ROMs but also it's stability due to more openess (for Google in its first place

).
Am I right?
Let's all hope.
If thats not gonna happen, for my next phone (whenever that's gonna come) I'll make sure the vendor supports project treble
Cheers