32Gigs is just NOT enough. I've been maxed out since the 3GS, iPhone 4 was a fail by not doubling the memory space so I've been maxed out this entire year too. I need 64Gigs.
If the chips are pin compatible, you could see if a company that does SMD rework could do it. I know Beijing iPhone Repair advertises being able to replace baseband chips. The flash memory chips should be the same process.