This was a request by Jaiden Bellet; so credit for the idea goes to them.
On another note; we've never seen this movie before. What's seen in the trailer is what we based our judgements on as to who was a villain or hero. 
Personally I thought Spike and Sombra's characters were Villain and Hero respectively, though the trailer seems to favor Spike as a good guy. 
Also, for Fluttershy's love interest; I couldn't stand to see any proceeds with that relationship knowing it was a love triangle, (from what I saw in the trailer), and instead put Discord as her love interest.