Although I expect that you can read data sheets: Up to 324-pin FBGA fits, also up to 484-pin UBGA, avaliable e. g. with Altera Cyclone III. If you want to have some other parts on the same surface, a 164-pin MBGA with 8x8 mm would be pretty small.
P.S.: Please don't tell, that you can't process BGA packages.
Although I expect that you can read data sheets: Up to 324-pin FBGA fits, also up to 484-pin UBGA, avaliable e. g. with @ltera Cyclone III. If you want to have some other parts on the same surface, a 164-pin MBGA with 8x8 mm would be pretty small.
P.S.: Please don't tell, that you can't process BGA packages.