hey guys,
I have the same scenario and I managed to do this in this way (It’s a little tricky ).
I have a RPI with Kodi in that TV and the RPI is always on ( not only when the TV is on ). If you have it connected via HDMI. so I saw that if I send a command to reproduce a video in the RPI, the RPI sends a command to the TV to turn on.
So, what I have is that when I want to turn on the TV, I just send a 5 seconds YouTube video to play in Kodi, this fires the TV on 
for me it works … not the best solution, but it works.