Transfer method I would use would be to just use a simple SAMBA/CIFS share that both the Amiga and PC have access to over Ethernet.
Personally, I just have a FreeNAS box with oodles of storage on it that's accessible to my pc's and Amiga systems running off an L2 managed 24 port gigabit ethernet switch. Have used it before in somewhat similar situations, but using Blender for PC as well as on my SAM with the NAS as the drop site for projects.
Obviously, you aren't going to get gigabit speeds out of a legacy Amiga ethernet device, but it should be plenty quick.
