Different experiences yes but the exterior presents itself like a haunted mansion. Building them right next to each other would seem off. Space and Tron don't look like each other so I think that works better. I also don't feel mystic manor fits the theme of that area of DCA unless they plan on redoing that area to represent that theme.
I wasn't referring to the exterior. Exteriors are easily changed. The HM in DL and WDW have completely different exteriors to suit their different locations.
Also, I don't think they look similar anyway. The HM is much less colorful and a completely different style. I see no obstacle to adding MM pretty much anywhere. All it needs is some minor tweaks.
I frequent WDW and DL but I'll probably never make it to HK. I hope they build MM in the US.