Its an interesting thought, but I Think Miraak is actually Konahrik. Please Allow me to explain. Now using my background as a historian and understanding of symbolism and Elder Scrolls Lore

(ES Lore is HEAVY on symbolism, not much is meant to literally, it is instead meant to be taken symbolically)

Now on to why I believe Konahrik is actually Miraak.

1. Konahrik is the only Dragon Priest missing from Skyrim...his mask has no body/Dragon Priest to wear it. This is significant because the Dragon Preist Masks were given to the Dragon Preists by Alduin in return for their loyal allegiance to his rule. All the Dragon Priests had many loyal subjects, and upon their deaths, these Ancient Nords buried and entombed these dragon priests with their masks...but not Konahrik...its like Konahrik just disappeared and abandoned his mask...why?

2. Konahrik is sealed/locked away in the past out of the reach of anyone else from getting it. Also, attaining the Konahrik mask is only possible by putting all the other 8 Dragon Priest masks on the altar as the key that unlocks the box. This "Symbolism" tells us this mask was locked away for a great reason...or a reason of great need...the fact that all the other dragon priests each held a part of the key to open the way to mask tells us that they each didn't want one of the others to be able to get it, and two something really important or bad happened that caused them to lock the mask away....remember Miirakk betrayed the Dragon Cult.

3. Look at the picture of the Konahrik Mask http://elderscrolls.wikia.com/wiki/Konahrik_(Mask)

It has tusks/teeth growing out of the face unlike all the other Dragon Priest Masks. This symbolism has significance because this mask, like all other masks, its an expression or a work or art. The Konahrik mask is symbolically telling us that its wearer is much "like a beast" or "like a dragon" due to the tusks hanging out of it, then the other dragon priests are. We know that only 1 Dragon Priest was ever DragonBorn and that was Miirakk.

So the only conclusion I can come up with is:

Either Konahrik is Miraak's old mask that he lost when he was defeated by Velok The Jailer, or their was another Dragon Priest who was Dragonborn....im leaning towards Konahrik actually being Miirakk..it makes sense...

1. Konahrik is the only Dragon Priest missing on Skyrim and Solstheim.

2. Miiraak fled to Apocrypha after being defeated by Velok (So he would be the missing Dragon Preist)

3. The design of the mask and the fangs/tusks coming out of it indicate its wearer had the qualities or aspect of a beast/dragon...we know Miiraak was Dragonborn and a Dragon Priest....there was no other Dragonborn Dragon Priests that I know of.....

either this is quite an awful coincidence, or Konahrik is actually Miraak's original mask, and Miraak got the mask he now wears in Dragonborn from Herma Mora. Thoughts?

IMO Vahlok was probably the last Priest to wear the Mask, but He was allowed an Honorable Death. The other Dragon Priests are tied to thier Masks to the point where they have become like anyone that wields Umbra, they have surrendered thier identities to gain immortality and Power through service to the Dragon Cult and Alduin.

I think Konahrik is either Vahlok, or it's just a title for "Hortator" of sorts for the Dragon Cult. Perhaps (a) Ysgramor wore it?

Miraak is Miraak.

Konahrik is Konahrik

Do the math.

And why would dragons give a Dragonborn a powerful mask.

Maybe he discovered he was Dragonborn later on in life. For example: Two dragons are fighting. One gets killed, since Miraak was in the vicinity he absorbed its soul, instead of the victorious dragon.

Since I first saw the Dragonborn trailer, I always believed Miraak was Konahrik. But then what about the other Dragon priests on Solstheim? They were never mentioned in Skyrim before the dlc.

Konahrik is an honorable title granted to one of the High Priests, by the High Priests under unanimous vote. Konahrik is whoever is chosen as a Warlord for the cult.

*facepalm* You do realize Miraak was part of the dragon cult for a time, right? As in, the dragons literally gave him a job.

As for Miraak being Konahrik, it's possible, especially since they showed that exact shrine during the Dragonborn trailer. It would make sense for a dormant dragonborn to be a good warrior. It would also contribute to his power hungry personality. Perhaps he was stripped of the title once it was discovered that he was a Dragonborn.

However, there's no direct evidence.

konahrik died a little bit after the dragon war begun we talked about it in another thread(cant really remember which)