Hm, somehow I failed to notice that. It's not clear to me that you want to avoid the edge effects, though; delegates might trade away influence on contentious issues (where we have significant moral uncertainty) to double down on settled issues (where we have insignificant moral uncertainty), if the settled issues are sufficiently important. Eliezer's concern that delegates could threaten to vote 'no' on something important would make others desperately buy their votes away from them- unless you have a nonlinearity which makes the delegates secure that a lone filibuster won't cause trouble.

[edit]On second thought, though, it seems likely to be desirable that delegates / the parliament would behave linearly in the probability of various moral theories. The concern is mostly that this means we'll end up doing averaging, and nothing much more interesting.