I don't understand why anyone would think 2 coasters or headliners next to each other would be a problem. As already mentioned, TZ and RnRc are neighbors. BTMRR and Splash Mtn. are also neighbors. My question is, once MK has 5, or more, very popular rides, do you think they will become a tiered park??
I think MK has never and won't (or perhaps I'm too optimistic) move to tiering due to the much larger overall number of rides/experiences that carry and disperse the load.
Also, am I only the luddite who has to constantly change "do" to "due?" Probably.