Redux G4:
I was seriously concerned about the difficulty of the level since I believe compilers have a weakness to fusion in Redux. I was not disappointed, however. Between added monsters and a steady stream of compilers teleporting in I was kept quite busy. Not to mention the challenge of the bosses. I should note that I got the boss hunter to get angry at a compiler which caused an odd standoff as shown in my first screenshot.
The sattelite dish blocked the shots of the baddies so they didn't hurt each other. Since I was low on O2 at this point (thanks, total carnage), I went to recharge, and when I came back, the two of them were still shooting the sattelite dish in some childish attempt to hurt each other. I was capable of activating the switches without having to worry about enemies. Of course, I cleaned the pair of them up afterwards since I didn't think that all of those shots the sattelite dish was taking were good for it.
Now, after the fact, I jumped down to get that stuff the Jugg was guarding and noticed a fighter teleport in!!! (see screenshot 2)
I don't think you are vacuum enabled, buddy. I decided to smack him with my staff since he didn't belong here, but when he died he exploded!
???
What's going on here? The staff on NBM doesn't explode fighters. I notice the staff explodes hunters as well, is it set to explosive damage for some reason when you hit things with it in vacuum?
I've noticed compilers show up as yellow on my motions sensor (at least, on this level. I didn't check NBM) Is this intentional?
I do generally like the staff as is: the odd knockback gives it a defining playstyle. I've read you can kind of fly with it (though I haven't tried myself), and would rather grenade jumping be the means of ascending heights. But it sounds as if you may have that covered by nerfing its ammo size (which I approve of).
I don't have too much to say about this level, since I really like it even before Redux and I think redux has done a good job with it. The only changes I might make have already been mentioned by others.
A note on difficulty:
I do think that Redux should be more difficult than the original. I've noticed that the Redux levels that I have played seem to have more monsters than the original, which is a change I approve of. I hope Redux continues this trend, particularly since some of the later levels (CS4S,C for instance) feel kind of underwhelming for how far you are into the game. I don't want the scenario to be nightmarishly hard (such as having to do a more difficult version of the pit on Cool fusion with just a fusion pistol, though admittedly I haven't tried doing that), but an increase in difficulty is definitely justified. Keeping on adding more monsters, bosses, etc and look for more ways to keep the game fun and interesting. I don't have complaints about turning a non-vacuum level into a vacuum one, I'm just not sure Cool Fusion is the level for that. If I recall correctly, Neither High nor Low may have originally been intended to be a vacuum level (according to some story page or something), so that might be a good candidate, I just haven't got that far in my commentary yet.
A good standard to figure out the difficulty of the level is if I comment on it. If I don't comment on it, it needs to be more difficult; there was nothing noteworthy in the level. If I complain, it's probably fine as is or maybe needs to be a little more difficult. I can't think of a level that needs to be less difficult except perhaps Bob-B-Q. Of course, combat can be adjusted as well, such as possibly SLN,TLC which was more annoying than difficult.
TL;DR Make levels more difficult, but not nightmarishly so.