Theme based on user group

[eteanga]

You could try, it might work as long as it doesn't conflict with MyBB's functions/variables.

Ok, I'm just asking for trouble including my own scripts.

I went back to your original suggestion. I installed the PHP in Templates plugin. Now this following works for me:

<if $mybb->user['usergroup'] == 1 or $mybb->user['usergroup'] == 5 then> 
You're either not logged in, or awaiting activation.
<else>
You're logged in, and you're not awaiting activation.
</if>