Problem with applying theme after enabling On-Screen keyboard

I cannot apply another theme than the default samsung theme after enabling On-Screen keyboard. I want the look and feel of the new Nexus that is why i enabled the on-screen keys and use third party launcher to theme and use stock lollipop icons.

I want to use the "Material Design" Theme but another problem would be the keyboard being themed. I only want the stock apps being themed by it. I hope someone interested with theming would be able to help me. Thank you in advance.