One can't really equate risking a life with outright killing.

Even if you can cleanly distinguish them for a human, what's the difference from the perspective of an effectively omniscient and omnipotent agent? (Whether or not an actual AGI would be such, a proposed morality should work in that case.)

If we want any system that is aligned with human morality we just can't make decision based on the desirability of the outcome. For example: "Is it right to kill a healthy person to give its organs to five terminally ill patients and therefore save five lives at a cost of one." Our sense says killing an innocent bystander as immoral, even if it saves more lives. (See http://www.justiceharvard.org/)

Er, doesn't that just mean human morality assigns low desirability to the outcome innocent bystander killed to use organs? (That is, if that actually is a pure terminal value - it seems to me that this intuition reflects a correct instrumental judgment based on things like harms to public trust, not a terminal judgment about the badness of a death increasing in proportion to the benefit ensuing from that death or something.)

If we want a system to be well-defined, reflectively consistent, and stable under omniscience and omnipotence, expected-utility consequentialism looks like the way to go. Fortunately, it's pretty flexible.