Idk, I think you could have your cake and eat it too though, do what they did for the dom heel turn, with a little tatanka heel turn sprinkled in. Here's how you could do it:

Saraya says she has to bring out the big guns, someone she's known for a long time and who has done it all. Both look pissed, but saraya is going with Mercedes. Then next week Shida tells Saraya that Toni is pissed and saraya should watch her back, or rather that shida will make sure toni won't do anything during the match while both are ringside. Then when saraya is looking at toni suspiciously postmatch, shida attacks her.

That way you still get to advertise Mercedes, and you get to set up this heel turn