I was thinking more to utilize Sareena at this stage is she's Quan Chi's real enforcer, opposed to the temporary enforcer Scorpion, who Quan Chi knew he would turn on eventually once Scorpion took out the younger Sub-Zero. Sareena at this point although she loathes him, in a dark twist is Quan Chi's real chosen one, in the same vein Noob Saibot is to Shinnok. The sharp blade to carry out their missions.
Putting her at odds first against Quan Chi's initial foes like Sub-Zero, then against Shinnok and Noob Saibot once Quan Chi betrays Shinnok, would've been against Scorpion once Quan Chi reveals his truth, and eventually against Quan Chi himself.

It's interesting how Dante's Inferno of Divine Comedy has levels of hell similar to the Netherrealm, the main similarity is Scorpion being sent to the fifth level, which is for those full of anger, very fitting of Scorpion.
http://en.wikipedia.org/wiki/Inferno_(Dante)
First - Limbo
Second - Lust
Third - Gluttony
Fourth - Greed
Fifth - Anger
Sixth - Heresy
Seventh - Violence
Eighth - Fraud
Ninth - Treachery
If this has any similarity, this had me wondering where exactly Quan Chi and Sareena reside. Since Quan Chi became weaker in the fifth plane and obviously wanted to get out.
Although it's likely a design change over time, I was wondering if the mechanical like Netherrealm in Sub-Zero mythologies was another level. Which has a lot of elements similar to Scorpion's current MK9 attire, very mechanical, even with the chain instead of rope. The level was pretty much metal platform after metal platform.
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What I think would be interesting is due to the elder Sub-Zero's high crimes of killing gods (water, fire earth) he was sent to the lowest level of the Netherrealm. Which on this is the Ninth level, which has a stipulation for treachery against gods. Which interestingly enough is an ice filled prison. Probably cold and dark enough to even put him in an endless torment.
If so, I imagine Shinnok took a sick pleasure in watching elder Sub-Zero's soul charged with such a weight. Especially because double crossing a satan like character has almost never turned out well.
On a side note, the way Noob Saibot can be explained is the actual name "Noob Saibot" is a title in a Netherrealm language for Shinnok's enforcer. A dark parallel of his once Sub-Zero title. As well as his pitch black appearance being from Scorpion's toasty fatality when he was killed, so full of rage Scorpion's hellfire torched Noob Saibot's very soul.