Sub-Zero
Scorpion
Raiden
Kitana
Kenshi

Raiden
Kai
Fujin
Bo Rai Cho
Shujinko

But at also want to see the return of scorpion, sub-zero, reptile, ermac, and baraka

Lol i ment 5 from each game to be the characters in mk10, so it would be 30 characters

it's a bit pointless, seeing as you've picked johnny cage from mk2 even though he first appeared in mk1, and kabal in deception, even though he's from mk3?

anyway:

MK1
- scorpion
- sub-zero
- reptile
- johnny cage
- raiden

MK2
- kung lao
- baraka
- kitana
- jade
- noob saibot

MK3
- sektor
- cyrax
- nightwolf
- ermac
- stryker

MK4
- fujin
- quan chi
- shinnok
- reiko
- tanya

DEADLY ALLIANCE
- kenshi
- bo rai cho
- frost
- drahmin
- nitara

DECEPTION
- havik
- ashrah
- hotaru
- kobra
- dairou

but that would be a TERRIBLE roster.

Honestly? I wouldn't want five characters from each game to return. That's thirty characters and I'm hoping we see some new blood. Sorry to go against the OP, but assuming that there are, say, six new characters and a roster of 30, that leaves only around 24 slots for returning characters. With that in mind, I'd pick:

MK1:

Scorpion
Sub Zero
Raiden
Sonya

MK2:

Smoke
Reptile
Johnny Cage
Jade


MK3:

Kabal
Stryker
Noob
Kung Lao

MK4:

Quan Chi
Shinnok
Kai
Fujin

MK:DA

Mavado
Nitara
Li Mei
Kenshi

MK:D and MK:A

Tanya
Sareena
Kira
Kobra