ok, i don't want to derail the thread, but i'll give my roster thoughts+ reasons off the top of my head (wall of text) based on the mk9 story line and personal preferences:
IN
scorpion - mk needs him; still lives on in the netherrealm in the mk9 storyline
sub zero - like scorpion, they need him; don't talk to me about frost, that bitch can gtfo; maybe reverse CSZ's cyber initiative-process, idk
ermac - don't remember him dying; might now fight for the good guys as shao kahn is dead
reptile - probably going renegade
johnny cage - alive and well after the mk9 story events, plus he missed enough mk installments as it is
mileena - yearning for the throne of outworld
sonya - obviously alive like JC
raiden - third survivor of the good guys; this time w/ better normals/strings
quan chi - raising hell and throwing a fit
kenshi - to make sure he's already in while they're still patching the game
OUT
kung lao - as much as i love this character, they killed him off good in the mkII arc of mk9 in a way i don't see him coming back
sindel - like lao, she was taken care off legitimately in the story line; also, she was never a favorite of mine
jade - never a big fan of hers, plus they obviously didn't get her right in mk9
nightwolf - cf. sindel
kano - LBSH, the character sucks; but give his choke move to someone else
stryker - i always thought gunshots to the face are stupid; defeated by sindel if memory serves
baraka - *yawn*
kuh-bawl - the king is dead, long live the king - but who will be s+ tier OP broken in this game?
CSZ - we had him, he sucked, next
sheeva - s.o.
freddy krueger - never should've been in there in the first place
MAYBE
liu kang - could be playable in a flashback of bo rai cho's; later in the arc as zombie kang; both skins for VS
kitana - a fan favorite, and as other characters in the battle against sindel, who knows if she lived; i'm undecided on this
cyrax/sektor - maybe only have one of the robots; i like cyrax better, but sektor has seen less games than his yellow buddie; tough choice
noob saibot - nobody knows what happened in the "soulnado"; i like him very much and want to see him done better in mk10
smoke - don't remember if he was killed, but i personally didn't quite like his playstyle in mk9; if he is in, get rid of his stupid hair
jax - like others who battled sindel, he was taken out quickly but might be alive; they rebuilt his arms already, maybe a more cybernetic jax?
shang tsung - given to sindel to increase her power, but maybe he could be regenerated during an arc w/ the now unchained ermac
skarlet - might be dropped for tanya's sake
rain - idk, this one feels iffy
i'll do new characters later, gotta go now.
TL;DR - there is no way to shorten this, so bite me.
