I will write something more about the aliens: The current alien is imho only scary when it is dark (at night, dawn or dusk) or when I forget to mentally "brace" against the scare. I think it took Luke an enormous labour to do it as it is now, but still it seems to me like a plush toy. I would like it to grimace believably, but it would imho require the facial skin to move believably, otherwise alien's face seems as if is made of a very (really very) thick, hard and inflexible skin which makes it a bit "impersonal".
But maybe it would be too much labor, I don't know. I suppose that even high-budget epic films (like Lord of the Rings or Star Wars prequel trillogy) could not create CGI characters with believable moving of face skin before this was achieved by a ground-breaking technology used in Avatar film
(for example in Star Wars III in the dramatic scene when the soldiers start to shoot Jedies, there are CGI characters which seem very unnatural to me in this respect, not convincig as living, breathing believable beings...) - so I have no idea whether making the face a bit believeable and grimacing can be feasible for a solo effort of one person with other commitments. I have no idea.
IMHO the original alien was extremely cleverly done artistically: who has seen a photo, he might ask "you call this scary??" But aliens's grimacing face full of teeth... Its moving and winging eyes, focused at me, full of self-confidence and intense hatred... The alien scare haunted me for years; I did not _remember_ these details but they certainly have a HUGE credit for the total effect... So the artists of the original game has imho done a wanderful job, but their task was much simpler than Luke's, because their alien had far less frames per second and far smaller pixel resolution than Luke's graphics.
Randomly generated features of aliens
Now I will suppose that making the fist impact more believable and making grimaces with moving skin would be too much labor - and so I will suggest something else: The alien scare is imho decreased by the fact that I know exactly what is going to happen, what I am going to see if the pilot turns out to be an alien. To counter that, the remake could have random changes. For example sometimes the alien will be shifted much to the side, sometimes it will jump less high, sometimes it will hit the glass from a greater proximity (his T-shirt will almost touch the glass) than other times; sometimes it will be overall bigger or smaller, or maybe deformed by a linear transformation (x->1.3*x, y->y). Sometimes the leap can be from longer distance (and take longer time)... I don't know: maybe such a long leap, if the graphics is done cleverly, could have an intensity, that the player would almost have a feeling that something (the alien or its fist) will fall through the monitor and hit him.
I don't know how much labor it would be to create several monstrously mutilated versions. Or it could have (with some random probability) horn(s), three possible shapes, many random colors and very different size. And (more or less independently on this), some aliens would have striking spots, scaring scar, disgusting blisters/ulcers - again: the shape randomly chosen independently on the color etc.
And something that could probably take less effort (but I am a programmer of algorithms with very little knowledge of graphics) and yet fulfill the goal nicely: Various parts of the alien (eyes, face, hands, shirt...) could have random colors (each part would, of course, have a different random formula because some colors are less suitable for eyes than for the skin etc...)
And as my experience is that the alien is more scary when it is dark, I try to think up how to use this if it is a day in the game. I don't know. Perhaps some aliens could have a color similar to the background mountains, maybe something like a mimicri. I don't know what would work.
And once the sound is added, it could also be randomly chosen from several possibilities. Lion road once, dramatic music other times, or sometimes with no sound effect...
Alternative ideas
I can imagine several reasons why these idea can be refuted: Faithfulness to the original game and the background information found in the manual (or maybe elsewhere). Or maybe it would be A BIT more scary if I did not know what to expect, but it would look VERY funny and ridiculous, degrading the game to something like a "cheap comics". Maybe the increase of the scare would not last long, because the player will get accustomed to what he can expect. (This could be dealt with by assigning some of the possible features a very little probability of occurence...)
Maybe the right way to increase the jump scare is to make the player more tense by making alien's damage
cumulative. Or by forcing the player to use much attention, for example by making the "evil" aliens visually very (but less and less with the difficulty level) distinguishable from "good" defectors that must be taken on the board. Or making some aliens knock the airlock with a sound very (but less and less with the difficulty level) distinguishable from pilot's knocking... Etc.
I don't know which of these ideas are reasonable. Maybe most of them are crazy and infeasible, but let's consider this a brainstorming where even crazy ideas are allowed.