It's not really a problem is it, you've got one of the top goalscorers in the league to 'force' into your team.
There are lots of options, people just seem to insult Cahill by insisting he can't play in a variety of positions. The only major limitation he has is that he's **** at defending. Frank Lampard's **** at defending. Tim could play any of the attacking positions to a reasonable standard.
He'd be decent on the left, I wouldn't mind seeing him given a go out there. His link up play's decent and he's a powerful runner with the ball, if not tricky. We've scored quite a few goals this season already where he starts on the left, lays it off and then charges into the box for the header. The only danger would be leaving Baines even more exposed, I can't really see Cahill tracking back and closing down as much as Pienaar does.
To be honest I'd rather see us go even more attacking and play him as the main attacking member of a midfield three. There aren't any rules against playing lots of attacking players, that's how you hammer teams. If we actually managed to sign the wing forward that Moyes apparently wants now, stick him up front with Saha and Beckford and play Cahill in front of Arteta and Fellaini.
If you think about the top teams, none of them would be worried about getting 'caught out' with a lack of defensive minded players, they're more concerned with scoring ****loads of goals. They even get criticised quite often for fielding a defensive midfielder at all. We have better attacking players than 75% of the league, why not use them all?