What's wrong with this schematic for powering up Cyclone IV FPGA?
Internally, the pad is electrically connected to the device GND pins, so connecting it externally to anything else is a critical error.

The Intel device page has a link to a packaging spec list, that links to a packaging spec page, that links to a pinout document, that has this footnote:

(4)  The E144 package has an exposed pad at the bottom of the package. This exposed pad is a ground pad that must be connected to the ground plane on your PCB. 
     This exposed pad is used for electrical connectivity, and not for thermal purposes.

https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/dp/cyclone-iv/ep4ce6.pdf