Cyclone V Core overpower effects

a) Operating the FPGA core above it's recommended operating voltage will reduce the life of the device. It's 'recommended' for good reason. Yes, I accept the absolute max ratings permit higher voltages to be applied to the pins, but no chip manufacturer, including Altera, are likely to support you if you run into problems.

b) Supplying VCCIO with 1.1V will clearly not damage the FPGA but will compromise it's ability to operate correctly. It'll not be able to operate at the fmax specified by Quartus; assuming it's able to operate it's I/O at all. I think (my feeling here, nothing quantifiable) the IO will operate at 1.1V quite happily at 1.1V and, providing you operate well below fmax, all may be well.

However, I would seriously question your need to save a voltage regulator. A solution to satisfy this need not be expensive. I accept if you're hand building a prototype you want fewer parts. However, as soon as it doesn't work properly - where do you start?

Regards,

Alex