It might help if you describe your requirements. Size, number of pins, ...
If you dont have enough digital IO you can consider shiftregisters or I2C/SPI port expanders. For analogue inputs you can use analogue multiplexers. This will make your design bigger.
If you're after something that is breadboard friendly there is e.g.
the Bobweeny (see Cross Roads Electronics). It has 32 I/O pins
This company also designed a breadboard friendly 2560; not sure if it's for sale (see Mega 2560 barebone - #13 by CrossRoads).
Although the owner crossroads passed away it's my understanding that the family did continue the business.
Neither of those has integrated bluetooth.