Summary: If you have an element of a game that is orthogonal to everything else, what are the costs/benefits from including changes to that element as different game modes? Parallel to this, would SC2 benefit from macro mechanics being a selectable mode?
Reading through QXC's post (external link: TeamLiquid) I was thinking about the overall topic, namely the recent discussions regarding the changes to macro mechanics. It got me wondering how the game would feel if eg. on ladder, in the same area we do map vetoes, you had a choice to turn on the original macro mechanics. Assuming some abstract mechanic doesn't skew any work a developer does to balance a game, does it really cost a developer much to allow players to play either with or without the mechanic? It would presumably add some additional amount of depth, and accomodate more play styles, at the cost of dilluting the core game play identity.
In the case of SC2, people may or may not feel the game is static. People might not actually want additional things to consider. Still, to use this particular case, changes to macro mechanics might not have to be absolute.