Can we include a small HTTP server (for .html + .js) into bitcoin? JSON-RPC will only work on same domain + port.
No, definitely not. But if somebody implements a nice Javascript GUI I'll volunteer to teach bitcoin to spit out JSONP in addition to plain JSON to get around the same origin policy...
RE: GWT: I'd prefer a non-Java-to-Javascript-compiled solution (shipping compiled, not-human-readable .js files makes me nervous; do we have to add all the GWT compilation mechanism to the build process? Or do we have to trust that you provided valid, not-messed-with, already-compiled .js files?)