Board Thread:Moderator News/@comment-28149328-20170308105554/@comment-27209138-20170309160148

In-game news said "Global Exclusive Units obtainable from Unit of Choice is up to Eerikki excluding Limited Edition Units, Raid Units and New Year Special  Rahotep "

And Feng is a limited edition unit.

That's mean you cannot select Rahotep or Feng as your UoC.