I'd do it. You have the RB depth and Smith would definately be an upgrade over your other WRs on your bench. Plus, you got to think playoff matchups here soon. Week's 15 and 16 (common playoff weeks), AZ plays Detroit and St Louis respectively.
I have Forte (who plays Balt and Min in weeks 15/16) on my best team, and I would be so tempted to start Beanie over him if I had him on my team for those weeks!
Make the trade!!