StormSkuggan, you are in the right path!
You have good ideas that gave me incentive to finally make an account to post into these forums. I have a lot to comment, but I'll focus on the "to improve on" because that's my reviewing style, but don't think that because I will speak little of the qualities I didn't liked what you did. I do like, and a lot ^^
Overall, if you do intend to label this ReMix as rock/metal, I feel the mix to lack the punch and the groove of these styles. What kind of do you have familiarity with Power Metal? Are you thinking more in the lines of an Angra, a Gamma Ray or a DragonForce? My cents of suggestion if you need a sound reference =)
The introduction for me sounds unclear, hauhauah. But to the point that I was unclear about if it should be unclear, and this "double uncleariness" seems to be in need of a direction
The hi-hats on the drums that begin at 0:12 sound to me as lacking humanization (and maybe another sample with greater quality can do great here). This is a universal problem to all your production, but here is a flare sign.
The electric bass that begins at 1:01 and the electric guitar that enters sound to me as in need of a better timbral treatment. Their section until 1:56 sounds to me as somewhat dragging; you could benefit for introducing more elements here to retain the listener's attention or/and, preferably, reduce this section in lenght.
At 2:23 you do a rittornello of the two main materials. In the actual shape, I don't feel this will work. Repetition is great and necessary to ensure musical form, but you need to do the second showing in a new light for it to not sound boring. The melodic variations of the source are cool, take them even further if you are bold to it.
At 2:51 you introduce the secondary material of the source. You alter the timbre of the lead melody a bit, and the rest of the rhythm section changes accordingly, but I feel it's not enough. You can enrich this by adding some instrumentation, giving the melody to another instrument, changing the equalization, and maybe all of this together.
At 3:15 you do a false entrance of the coda of the source material in a 3/4 meter. Man, this is awsome. You build this great formal energy that grows into a... Repetition of 1:56 at 3:29? For me, this was very frustrating :/
From 1:56 to the previous section, speaking of OCRemix Submission Standards, you may run the risk of staying too close of the original source, in terms of the order of the materials.
Then in 3:29 you expose the pair of main materials again, but in a way too similar to the previous one (no significant changes in instrumentation, lack of SFX, same timbre in the melody, etc). And in 3:56 you go to the secondary material, with great melodic variation.
In 4:21 is my favourite moment. This suspension with the arpeggios from the piano are marvelous. You can enchance this to even further highs with better production / mixing techniques, but the idea is awsome \o/
Then in 4:34 we finally have an extended coda. You can work better the rhythm section in terms of energy and more notes to make it feel more "codastic". This moment is the upward strike, but there are other moments in the music that have more momentum than here, and that can be improved.
The warping portal you open at 5:04 is a marvelous idea, and ultra innovative in terms of remixes in this site, and the reason you convinced me to give all this attention to your post. But I feel you can execute this idea better. The transition from the coda to it sounds strange and unclear, and the the following chaotic motions of the voices are cool but lack the vortex-y feeling of what is happening. You need to put more sound effects here for it to really work as intended.
Speaking of sound effects, if you are really in the rock/metal vibe, if I'm allowed to suggest a Progressive Metal project, check out the last Ayreon album, "The Source". It has a lot of great SFX, and in great variety. The four last tracks can give you great ideas of what to apply here =D
Well, sorry for the wall of text. This is my first post, and I got excited, but I do hope it's useful XD