I've got the LG Optimus 4X HD (P880) and its unofficial here. In official Roms you can download updates via OTA and then I thought it will be nice if we had it. So I ask you is it possible to make this phone official?
I'm sorry but you are all wrong in this case.
First group of MIUI v5 devices where those that already had MIUI v4 Jelly Bean. And its One X, Gnex, SGS3, Note2 - and those are supported till today. Optimus 4X HD got Jelly Bean only in... 2013 - where all other devices got JB back in 2012. Its LG fault that updated its devices to JB so late. Xiaomi said clearly that they will be adding only 1-2 top devices per manufacturer. LG is not a top device today - its 2 models old (Optimus G and G2 is newer).