I would keep:
1. Gameplay Engine
-The gameplay felt the best out of all the 3D MK games, so no need to waste time coming up with an all new engine. Just tweak the one already there, and just apply polish anywhere needed to make it run smoother.
2. Freefall Kombat
-This seemed to fit in well during transitions, and I don't see the harm in making that part interactive as opposed to not.
I would change:
1. Make it darker.
a. Gore:
-I know it was going for a T rating, but this time around I want it to be dark, edgy, gritty, and shocking. MK used to set the standard for violence and edgy themes. What's considered "dark" and "violent" has changed since almost 2 decades ago, so it's time to ramp it up. I want to see dead bodies throughout levels. I want to see blood used in all kinds of ways, but only where it's effective, not just for the hell of it. Dead animals, dead children, dead babies, severed limbs, people hanging, skeletons, crap, vomit...I mean anything. Make it make sense though. No 10 torsos sitting in a room for no reason other than to be "scary". I want to feel bad about playing this game.
b. Levels:
-I want the level design to be creepy and dark. I almost want to say the word "distracting" to descibe how they should be. Environments that make me want to look around as I figh. I want it to make me feel nervous, uncomfortable, and eary just looking at the background as I battle my opponent. I want slaughter houses with dead animals, prisons where the inmates are spewing curse words and throwing fecal matter, insane asylums where they are killing themselves or sitting in corners talking to themselves, morgues with dead bodies and an incenerator, battle grounds with piles of bodies on fire, wastelands with skeletons of animals and people etc. This is some creepy shit. A graveyard with a moon shining down and some tree silouettes just doesn't cut it. Not to say you can't make something like that creepy, but they are way too clean and bare to make it truly unsettling.
c. Fatalities:
-I want to see some really ****ed up stuff along with what we normally get. I recall seeing Reptile eat someone's face off in MK4 and thinking "That's creepy." More of that please. Kano ripping out someone's heart, and then either eating it himself or shoving it into his opponent's mouth. Tearing someone's jaw off. Cut their tongue out. Not all have to be that disturbing, but have them at least be brutal. Such as Quan Chi ripping his opponent's leg off, and then going on to beat them with it. That's not as shocking, but it's vicious. More anger and brutality in their fatalities. Have Raiden grab the opponent by their junk and electrify them, only for them to fall on the ground and then have the MK cabinet fall on them. That sounds a bit childish, but the MK team usually likes that kind of potty humor, but IMO it gives a very torturous feel to it. Another example is have Baraka slice off each limb 1 by one, and then cut of the head and put it on his blade and show it to the camera. That's a dick move, but it's a battle to the death, and Baraka is an evil asshole with a lust for blood, it just seems right he'd want to make his opponent suffer more. Make the player feel like these guys really just want to destroy their opponent.
d. Attires:
-I thought the attires in MKvsDC were a step in the right direction. Most of them felt a lot more realistic and dark. They looked a lot less cartoonish/plastic like, and came off gritty. Keep going in that direction and just do everyone's model/attire like that. No more showy or flashy designs, only for alternates if they desire, but everyone should have a serious gritty appearance for at least their main attire. This also means no more sexy unrealistic battle attire for females. MK should be pushing the M rating it's fullest, but not because they want to give the girls skimpy attires with realistic boob physics to give all the nerds somethin to picture during their lonely nights. I'm not saying put a sweater on 'em, I'm saying no more bikinis, bras, thongs, or high heels etc.
2. Better Levels.
a. Too empty:
-The level designs in MKvsDC seemed so empty. I want more destructable stuff within the arena they fight in if it makes sense, such as inside environments, so it seems much more realistic and it's just visually interesting to break through stuff. MK
eception did a great job in some of it's levels with this stuff such as in Beetle's Lair.
b. Death Traps:
-Stage Fatalities were great, but I just don't see how practical or plausible they would be in a 3D environment, with that being said...I thought death traps were a fun addition to levels, and offered a nice visual both in the background as well as the animation of someone being killed by one. Obviously there were some dumb ones that were silly and didn't fit, but then there were others that were just plain awesome to see. The human grinders in the Beetle Lair was very fun to see your opponent get knocked into, as well as the steam roller one in MK:A's armory. These should come with an option to be turned off, as I understand they aren't for everyone, and another option for them to actually end the match rather than just the round, and they should be harder to be knocked into requiring the victim to actually be closer to the zone than previously, thus making it more rewarding when it happens.
c. Weapons:
-I really enjoyed when the stages had weapons, it was another thing that could completely change the way the battle was played. Of course I am one of those people that can't help but spend half the match trying to manuever my way over to grab the weapon, regardless of the fact that I usually get my ass kicked in the process, but that's all part of the fun. Everyone loves options, and if people don't like the weapons, they should just be able to manually turn off all weapons, or just individual weapons for certain levels.
d. Interactive and Diverse Environments:
-I stated before that I would love to have all those gritty, dark, and disturbing places as level environments, but that doesn't mean every level needs to be that way. I would love for some more diverse levels with some actual interactions between the fighters and the environment itself. A field where there's tall grass that you actually can't see the fighter's bodies from around the waist down(I believe Tekken had a level like this in the dark with moonlight, definitely a stunning visual). How about a level that was previously supposed to be included in I think MK
A, where the fighter's are fighting in a small shallow pond/swamp of sorts, and from the knee down it's water, and have it be morning with some fog and trees/bushes etc. in the background. Those are just a couple of ideas for interactive levels.
e. Changing Levels:
-I was a HUGE fan of the concept of the Falling Cliffs level from MK
. I just loved how you had to constantly be aware of the outskirts of the arena, and if you were on the outer parts of the circle you needed to manipulate your way to the other side of your opponent, if not you would fall to your death. More stuff like this where the level can morph and things can change and possible open up more parts of the level, or certain parts become dangerous at times like an avalanche, falling rocks, cars, animals etc. that go through part of the path and can hurt or kill you.