Yep. It'll work just fine.

Why, though? It's not going to shift noticeably better. I've got everything from 4600 to Dura Ace cassettes, and I don't notice any shifting difference between them.

Weight? Get a 105 cassette and scarf up an excess alloy Ultegra lockring to make up the 1.5g of weight difference between a 105 and and Ultegra cassette.

Do you really need the 11 instead of a 12? What cog do you give up? (I'm too lazy to look.)

If you need a replacement, just stick with 4600. I've got several that I use in races - an 11-25 is a great one to have for some races.

If you want to improve your rear shifting, find a Dura Ace 7800 RD cheap somewhere. Works great with 5700 shifters.