I finished this level a day or two ago but just now redid it to get the alternate ending. Here is my feedback regarding this ending:

On my first attempt I thought that the red keycard would be somewhere within the zone that you reach by elevator. This was because of the reference to the red keycard appearing as you go down the elevator, and no mention afterwards of the keycard (at least until you're near the end of the level). Because of this I spent some time searching the area unreasonably thoroughly thinking that it would be hidden somewhere in this zone. I had to look at Skummeh's playthrough (posted previously in the comments here) to find where the red card is. I don't know if its location being way behind is intuitive to other players but the thought that it could be where it was never crossed my mind. To this I feel there should be some hint of the broad area it is in, seeing as how the level currently made an impression that it would be in the zone reached by elevator. Of course, it should be a subtle and not obvious hint, but nonetheless one that would enable someone moderately committed to find the keycard.

Otherwise, I found part 2 very much improved over part 1. The best improvements I noticed were the better lighting (the biggest improvement imo) as well as the improved variety of environments and little details. Both this and part 1 don't make you bother with resin which I like, to me dealing with upgrading feels like too much hassle unless a level is mini-campaign length (like C17YSCAPE) or something non-standard like zombie wave defense. Combat was also just as fun as the first part. Ammo is scarce but not excessively so, by shooting carefully and keeping my eyes open for ammo I always had enough for any encounter. If anyone is having trouble finding enough, ammo seems much more common on easy (I played on easy on my alternate ending run, not my first proper run!!).