The answer to this question according to Tigers' management is third base. He too prefers to play at third and considers it his natural position (or so I read somewhere). Reportedly he has been instructed to "get into 3rd base shape". He is considered too fat to handle the hot corner.
But is he really so overweight as experts think for such a move? A couple of examples indicate quite the opposite.
First there is Adrian Beltre. Beltre stands 5'11 and weighs 220lb. That would make him even more overweight than the 6'4-240lb Cabrera, and yet Beltre is a multiple Gold Glove winner and rightly considered as one of the defensive third basemen.
Then you have Scott Rollen. Rollen is a 6'4-245 multiple Gold Glove winner.
By the way Beltre is already 33 years old and Rollen 37 but their defense does not seem to have suffered that much. There are a few other examples of players that clearly do not have the optimum weight but nevertheless are considered as at least average fielders at the hot corner, with the more outrageous of them all being Pablo Sandoval of the Giants (5'11-246lb).
In this sense Cabrera's size doesn't seem to be that important. He just doesn't have what it takes to stick at third. Everyone in this community to would love to see the opposite happen and Miggy silencing all his critics, but the odds are against him. It's a pitty but it's also the truth. Remember that Ryan Raburn was also a third baseman when he came through the minors. But who can reasonably trust Raburn at third?
The team does not need to move Cabrera at third at this time. Remember that Brandon Inge is still a very capable defender and under contract for this season. While he was terrible last year, people seem to forget that bout of mononucleosis he suffered early in the season and which might have affected his performance more than he would admit. In this respect I think that a healthy Inge can put up a solid season not only on the field but at the plate as well.
So my suggestion is to leave Inge at third to fortify the left side of the infield along with Peralta and (for now) alternate Cabrera and Fielder at first base/DH.
As for the next two years when V-Mart is back, I would say to move Cabrera (or maybe even Martinez) to left field where his weak defense will not matter that much and replace the departing Inge with a temporary stop-gap until Martinez's contract expires and that you-know-who prospect is ready to take over at third, in which case Cabrera and Fielder can return to alternate between 1B/DH.