I admit this idea was thought of before MK9 came and established a new timeline, but it can still work within it.

Like in the old timeline, the Outworld Investigation Agency is created as a counter measure against invaders from other worlds, along with the portal technology. However, it's also used for other purposes, such as searching for anything that could be of use, especially things of financial worth. Another thing they look for are races to enslave. Tarkatans are among those.

Many Tarkatans are captured and taken to Earth. The government has no problem getting the majority of the populace to agree with the Tarkatans' enslavement, given their role in the attempted invasion of our world, as well as the fact they are are scary-looking and seen as more beast than man.

This story could of course be used as a way to develop Baraka (and perhaps Mileena too) or to introduce a new Tarkatan character (preferably a female one imo), or both. If both were done, then both Baraka (and Mileena, if she's involved) and the new Tarkatan character would play a role in a uprising against their oppressors, but with different opinions on how said revolt should go.

The main villain, whoever it is, could try to exploit the Tarkatans' plight for his/her/it's purposes. Sonya could find herself rebelling against the government for what they've done. There's other consequences mankind's actions could bring, other familar characters it could affect.

To conclude, The Tarkatans would be clothed with slave wear, which in my mind is basically orange prison clothes, with short sleeves given the Tarkatans' spikes and blades.