Tv stand by fireplace help

Hello.

The situation:

I will be moving into a new apartment soon the place looks great but there is one issue. The only wall to place the tv has a small fireplace right in the middle of it.

I had hope to get some ideas on how I can mount a height adjusting tv stand by the fireplace so then when I am not using it I can have the tv at a normal height instead of cranking my head back. I do want to use the fireplace sometimes but being in Arizona the chances will be lower than other place.

The idea I had was to possibly build a stand or some sort of locking track where I could slide the tv up and down in order to easily switch between "normal viewing" and "fireplace" modes. One idea was to have a large shelf on each side with a track on each that a board would be connected to, then attaching the tv to the board.

Any suggestions or ideas on how to build this or how to make something better? (I would also put a heat reflecting surface/board below the tv to keep the heat away while using the fireplace.

the picture enclose is the one from their site due to me not being able to take it myself.