Having Trevor suddenly becoming a thread is an aweful, aweful idea. I didn't like it but Killian is right now the films version of the Mandarin, continue with that.
If you don't want killian then why not introduce a chinese business man named after one of the Mandarin's alias in the comics, this way he wouldn't be considered racist due to his name and we would get the character without retconing Iron Man 3. Yeah i know it would mean another businessman villain but that's the best way to fix things without continuing with Killian, the Mandarin has sort of been reintroduced in modern comics this way.
Though in my opinion they should go on with Killian, he has powers and organizations, and his "death" didn't look like a death at all.