If you like crazy soldering exploits, check out this PSP reverse engineering hack, where every pin of a BGA was soldered to magnet wire.

The eMMC used has two power supply lines: one for the memory and another for the interface management hardware. If the interface power supply is at 3.3V, the chip can’t support the faster modes.

The original Nexus 5 was never offered in a 64GB variant, but that didn't stop one owner from making it happen by soldering in his own replacement EMMC chip.