I'd like this so long as they differentiate them somewhat form regular open areas. They'd need to have some purpose (in my opinion). In FFXI they existed, but there were few differences between dungeons and open world areas. Mostly they were 'inside', the spell 'escape' worked there, and there were coffers that could appear somewhere on teh map (and be opened with a key that dropped from certain enemies within). Outside of some quests and things that required you to go there and do something specific people just treated them like any other zone -- that is to say some were ignored almost completely and some were used heavily for experience camps (not something we have in XIV).