Multiplayer support is seen as a must-have feature for a lot of reviewers and many players (especially those coming from the action RPG or MMORPG parts of the RPG spectrum, or from RTS or FPS games). Dropping multiplayer might speed up the release, but probably at the cost of less sales and therefore less chance (or slower release) of additional RPGs from Larian.
An editor would probably have much less of an impact on sales (and reviews, for that matter), and the effect would be a while after release, when the price has dropped and people have had time to create additional content.
In any case, this is irrelevant to whether or not an editor is wanted.
