Have you thought about maybe just talking to him? I know that gaming in general, and at times it seems Shadowrun in particular, has a long and proud history of, instead, custom tailoring encounters and NPCs to counter a player character's latest trick and keep things challenging, frustrating, or somewhere in between...but...
Why not just tell him you've got some misgivings and concerns about this new mage, before gameplay really starts and he gets attached? Because "this is what I have to deal with as a GM" strikes me as a pretty unfun attitude to have. If this new character's shooting your enjoyment in the foot, if it's giving you headaches, if you're worried it's going to be too good or too bad or just too lame...or whatever...
I mean...talk to the guy. Gaming is a social activity. The people in your gaming group should be your friends, at least to the point that you can talk to them about the game, rather than only being able to talk to them in the game. I'd tell him your concerns -- now, early in the week, when he's hopefully still got time to work on a character and be excited about it, not right before the next session is supposed to start -- and ask him to make a few changes, if I were you.
Talk to him and find out what it is he thinks makes a combat-paralyzed mental manipulator (with a club, not a gun) awesome, instead of irritating or just weird. See what it is he digs about the character concept, see what you can salvage of it so that he'll have fun, but not at your expense (or everyone else's), and hammer out a cool character that you'll both like. Now, before it's too late, and he's put even more work into it, or gotten even more psyched about it.
Life's too short for stress to ruin your leisure time with friends. This is something you can nip in the bud pretty easily, seems to me. No need to let it fester and then be all passive-aggressive about it.