You can synthesize a 6502 on an FPGA just fine and can probably do it on this specific chip. There is a project I've seen (https://danstrother.com/fpga-nes/) where someone did synthesize the 6502 along with the rest of the hardware on a Spartan 3 which does have more resources available to it. Looking at the utilization report in the comments on that page, it would be too much for this little Lattice chip. There are other FPGA development cards out there similar in size that would work better for your idea. You would be better off getting a larger development card for designing and then moving to some custom PCB that fit only the components you need at the size you want.