I have just realised that you don't tell us if you have warranty... if you have it then use it. Cause the way I've told you before probably will void the warranty.
I don't know how it works in your country but here in mexico, there are several External Service Centers (not official) they repare anything, softbrick, hardware brick, change the case cover, dialpad, etc. but it has a cost. If you buy the box just to repair your phone I think it will cost a lot of money to you since this boxes works with a lot of models of different brands (they are expensive) and you need technical knowledge about how to work with them.
In my case, the Service Center first tried with riffbox (cheaper and fast way) and it worked to turn on the phone in a couple of minutes, it was indicating there was bootloader broken so it worked when tried to rapair it but since my emmc memory was kinda buggy, it died the same day, so i left it again to warranty on the SC and they then tried with jtag this way they told me is like the "hard reset" since wipe and make again the partition system and install all the stuff, now works pretty well but they make a warning to me abut future deads because the final solution and the real one that needs my phone is to change the motherboard (they don't change just the emmc).
But if your emmc is ok, they probably just need to use riffbox maybe jtag but your phone will surely be ok again.
the cost for the reparation should be about 30-50 USD
If you don't know where is one of this external service centers on your town, try searching on google about riffbox, jtag service center in -your town-.