Currently, the command source is always centered around the chance cube block, with the direction [for things like ^coordinates] set to the player's direction. A way to customize the origin point to be around the player's position, at the least, would be useful [for a command such as "summon a creeper behind the player"]

[I can't think of any other things someone might want to use as the origin, or anything other than the player's facing for directions, but leaving it open for future expansion would probably be useful]