The Rays are working out at The Trop today (how good does that sound), and among those taking grounders at first base was Joyce (per Marc Topkin of the Tampa Bay Times). Of course, Reid Brignac also took grounders at first base, so maybe we should temper our excitement.
Still, as a lefty with a little pop in his bat, Joyce would make a good first baseman. And if he can adapt defensively, it would seem the Rays would have an easier time finding a new right fielder (maybe some combination of Sam Fuld and Brandon Guyer, if all else fails).
Of course, we have seen the Rays experiment at first base before without success. Ben Zobrist spent a lot of time working out at first base last winter. But when the regular season came, he never found the proper level of comfort and never played the position during the season.