Yes, it is certainly possible to solder 64 pin QFN chips with a normal iron. It's just that less people know how to do it.
I suppose my biggest reservation about the STM32 is sort of a nit picky thing: It really doesn't come with the source code to the FOC library. The hardware of this device is open source and I think that the software should be too. Microchip has freely available source code right on their website for FOC. I need to check into it more but I don't see it being a problem to use their code in an open source firmware.
The STM32 code also seems heavily geared toward PMSM drive. That having been said, it does appear that the library probably supports async ACIM too.
I guess I'm just leery of using a black box. The STM32 code is all packaged away and you are just supposed to trust that it works the way you want.