Change emojis or downgrade from Android 6.0

Hi,

I have a HTC One M8 and the new Android 6.0 update was released for it a few days ago. I thought it would make my phone better (as most people think) but realised that I hate it on extreme levels.

I hate the new emojis released for Android 6.0.

Because of this, I want to downgrade from 6.0 Marshmallow or change the emojis.
Is there any way to do this?

NEW: I have download some keyboard apps which change the emojis but they only change the emojis on the keyboard, not on the system :P

Thanks.

Download from this link