Granted, you can't drive a substantial load with a 5-volt MCU either. However, you CAN drive a logic MOSFET and IT can drive the load. With 3-volt logic you have to drive a driver and only then have you enough voltage to drive a low-cost MOSFET. Once you start fudging with resistors and diodes, etc, the cost advantage associated with those FPGA's goes away. It's not that large anyway. BTW, I do know the difference between VccInt and VccIO, though, as you say, it's just a detail. However, the relative ease and low cost of driving hefty loads without adding extra components such as level shifters or even series resistors and clamps, is one thing that keeps the 5-volt MCU's alive.

On the other hand, you can use a $2-3 5-volt MCU together with a $2-3 (depending on your procurement skills) 5-volt CPLD, though they, too, are becoming scarcer, perhaps with a single <$1 SPLD to select which CPLD (The really big cheap ones seem, predominantly, to be available in PLCC-84 and have about 64 I/O's, so you'd need two in order to handle the 136 loads.)

The FPGA's have their place, and are very much at home in portable and other low-voltage applications that don't require lots of power. Of course, what I think is practical isn't going to change what the FPGA mfg's think is easy and profitable. In the meantime we'll just have to wait until there are more low-voltage logic MOSFETs, which will cause their prices to drop.

RE