around quest TR_m2_FG_Irano4: once borderline but self-aware dialogue about "Valley of Mephala" now nonsense due to the region synonym,
area that was "Valley of Mephala" in earlier files now appears in clear daylight ruining the ambience, must be worse if MGE used,
besides dialogue consider separately whether it will need to have a name restored as region &/or cell name
(if region: before simply reassigning all previous cells note that the area didn't sit cleanly within borders, might lead to the name displaying outside of it even with buffers;
for cell name, if you want to use "shambalu" in the usual daedric exterior fashion, mind that the interior already uses it without "shrine";
the area's fog/rain weather can only be restored by region or script),
in generic dialogue some leftover Mephalain/s (Mephalan WITH the dumb celtic "i" from previous name);
"Mephalain Mountains" in cell names only a couple shacks;

+ just overall consequences of taking terrain that was built to be called one thing and calling it the opposite thing, this isn't really quantifiable

yes, for instance first CS search result on "sea of ghosts" is topic "boethian mountains lighthouse", cell also with a previous region's name,
some more leftovers in dialogue that didn't get edited, on the other hand as some dialogue DID get edited do their topic links still work?
topic for sea has itself
"The Sea of Ghosts is the sea that surrounds most of Morrowind. It is to the east of here."
likely given west of what was renamed, ... etc