I think you’re always going to want to do at least the V x I dot product at the pointy end, just because of the sheer volume of data and its need to be carefully timed so as not to introduce phase errors.
There was some very early prototype work done on that a few years back: STM32 Development
I was wondering what had happened to that project. @danbates is that project still a going concern or has it died out?
A more modern Cortex-M based processor is way cheaper than the old 8-bit AVR stuff.