Just out of curiosity, would it be possible to use a lot of RAM and treat it as an FPGA capable of mining other cryptocurrencies, or would it be too expensive to implement and not worth it?
The statement "treat it as an FPGA" doesn't make sense. Both RAM and FPGA (or ASIC) are electronics but that's where the comparison ends. RAM is designed for one specific task and cannot by itself do calculations required for mining.
Your CPU would still be performing the calculations, and so you'd see a slower speed than if you used a CPU miner.