The next fit did happen and I followed through. James watched while I packed up every single one of his Lego ships, every Lego guy, every brick. He took it very well. Too well. He started to HELP me. (Mommy note: I started to think, This isn't working. He thinks this is fun!) But at least I followed through and James would see that I meant business. I was TOUGH.
I decided that I would get a bit more creative with the consequences after this. It was A LOT OF WORK packing up all these Legos and then hauling them upstairs out of his sight. I didn't want to just throw the Legos in a bin and risk breaking the fragile ships (i.e. more work for me later to put them together) so I carefully put them in bins, on a tray, and even used my triple decker cupcake holder for the smaller creations.
So the behavior improved. The Legos were barely missed until later that night. James asked for his Legos back. (Success!) I said no and reminded him that because he had a fit he had a consequence and he would see his Legos tomorrow. He accepted that pretty well and we found other toys to play with.
I haven't had to take away Legos or any other toys since. I don't think it's just because I got TOUGH one time. I think it helped a lot that he saw that this Mommy wasn't going to put with that s#%@! I think we've also been much more consistent and followed through with our discipline. No means no, Later means later, and sometimes You need to go potty first or Eat your food first means just that.