Anyone have the rest of this doujin? It seems like an interesting "what-if?" scenario.

What I saw had only two pages, this and the next page, which goes nowhere.

This is the end of the doujin where Rin summons Gilgamesh. Anyway, Caster'd probably just kill Shirou.

Penultimate page of "Gilgamesh VS. Rin", you can get the whole thing at Gaku Gaku: http://www.freewebs.com/aortic/index.htm