In a word, no. 

If I wanted you to have ultimate powers and play demigods I would be having everyone play chapter heroes, maybe head of the librarium or something similar.

You are scout marines. Not full marines and not quite as capable as them. If you try to go toe to toe with a bloodthirster or chaos lord you will lose. 

As for psykic powers in general.... Let me think about that. I'm not against the idea of your geneseed awakening psykic talents. But they would be lesser degree psykic and very much unrefined. You may not even know you have them at first until something snaps inside your head during a stressful moment.