It could be done, there just one problem with the only character with lots of new sprites: Johnny Cage.
That could be done resizing their sprites with waifu2x or something like that, I think the MK1 have some badly done new sprites but its not that much work like JC could demand.
Yeah, I thought of that though I would almost be inclined to just drop the MK1 and MK2 variants of characters which mostly solves that problem. Those variants are a cool novelty but it was always weird to me that it was only for a limited number of characters so I say cut them. Maybe include MK2 Jax for the novelty of having human arms Jax and and metal arms Jax? Then for Johnny Cage use his MK2 sprites. I guess that means leaving out his back breaker fatality but that kind of sucked anyway. I guess they did add new animations to Goro, Baraka and MK2 Raiden but a lot of that stuff is minor.
Wait so, WB/Midway/NRS had zero input on this and did not approve its listing. GoG can just list any titles it wants and I would imagine pays royalties back to WB? Seems hard to believe they don't need a license, as this would be copyright infringement. However, the shitty artwork for the other titles makes me think it is not official. And apparently there are some assets from fan made patches, which could be a security risk.
No no no, they work with the publisher but basically with releases like this my understanding of how they work is: gog gets the publisher to sign off on making their game available on gog along with agreeing to whatever sales split and they get assets along with the game from the publisher but once that's all agreed upon gog kind of takes it from there and does all the heavy lifting. Which is important because if the impetus was on Warner to make these PC versions available… these PC versions wouldn't be available. But Warner is happy to make money for doing nothing.
That's why these aren't on Steam. To release these on Steam either Warner or Valve would need to do the work to make them available on there and that's not going to happen. Also if you think all fan mods and patches are a security risk you must not play many PC games. Gog is not some fly-by-night operation, they know what they're doing and they research this stuff thoroughly. They've been around for years and are owned by the developer behind The Witcher games and Cyberpunk so gog isn't some unknown entity. They're a very well established PC storefront. They're not going to put something for sale that's a security risk to their customers.
You just need to know what you're getting into when you buy games like this from gog. Gog did the work to get this game running on modern hardware but the impetus is on the user to get the game running how they want it. You're probably not going to be installing this game and just immediately playing it how you want, you'll probably need to tweak some settings.
Basically gog used to stand for Good Old Games with their goal being to sell old games as well as take old games that no longer work on modern hardware and make them playable on modern hardware, DRM-free. This was partly born out of the number of old games you could buy on Steam that just won't even launch on modern PC hardware without at least installing mods or modifying game files in some manner.
For example, I own Street Fighter X Tekken on Steam which does not launch on modern PC hardware without mods. If that game were made available on gog they would either do the work to make the version they sell launch on modern hardware or they would at least pack in the existing fan mods that do this work. Sometimes they take things a step beyond and include stuff that modernizes a game in some way but generally there only goal with old games is making them playable on modern hardware without the consumer needing to do anything. Anything beyond that is on the consumer to take care of.