Nice ambient soundscape. I actually think there are problems in the EQ and playing though that make it fatiguing and loud, and additionally overcompressed.
The piano starting at 0:13 is grating in that it has a resonance and it is somehow sustained in a such a way that it sounds more like a synthetic FM piano, and in that sense it hurts.
At 0:51 - 1:19, it's most evident that the guitar has several moments where it has an isolated loud strum, and I think it's too loud compared to the rest, which for me, detracts from the strings padding that is laid out beneath the guitar. It's also a little stiff.
These two above issues apply throughout wherever they appear. At 2:18, the vocals are indeed pushed back too far, and they are actually saying something, so understanding them is important. I can't understand them.
Interesting shift to metal at 3:03. I think that was well-executed in terms of the arrangement flow and transition. I do however think that there's a distinct lack of bass presence until 3:32 or so. At that point it seems like the bass just creeps in under the radar, and it doesn't feel natural to me. I think it'd be better if the bass was foreshadowing its presence more obviously. It also seems that there are vocals at 3:36 that are completely buried. Unless that is somehow what you want, I don't think that they are necessary there. Personally I wouldn't purposefully hide vocals, in any situation, even if they are merely backup vocals.
Overall, the ideas are good, and they make sense in this context. You have a soundscape that is sensible and coherent, and this is a plausible approach to an ambient/metal remix. I do think though that the slight overcompression (not extremely noticeable), the grating resonant piano, stiffly-played and occasionally loud guitar, buried (unintelligible) vocals, and overly subtle bass entrance detract from this too much. I think this is salvageable, but there's a lot of detail work associated with it too.