To answer your question, yes it is indeed possible to banish a troublesome player to a Mystcraft void age. I would suggest running your plan by the server admin or at least an OP before getting yourself banned.
Edit: I can't stress this enough - make damn sure you aren't the one losing out on this. Check with the people who run things.
I would use some sort of player detector opening a drop trap in your floor (disguised to not stand out, of course) with a Mystcraft portal active beneath it. A narrow hallway with a bait chest (crystal chest with a diamond/emerald should be enough to get attention) at the end. Extra points if you "hide" the entrance to the trap to dissuade suspicion - enough to make it seem like you tried, but not enough to actually hide it.
Depending on what tech you have available, I believe RFTools can block flight in a limited area at the cost of RF. If the portal is only a block or two down, he may not have time to react anyway, but if you have one goal, do it right, right?