[plamzi]

"Portals" are only the simplest link that "freeform" MUD rooms can have. There's also compression, loops, "multi-jumps", whatever you want to call them.

If portals are the most you're willing to bend the spacial rules, then sure, you can enforce a grid throughout and add a single special case.

A division between "travel/roam" and "dungeon" can be useful even if you enforce a grid for both (with small exceptions). E. g. a "roam" area will create a room dynamically if a player strays from the beaten path between A and B, whereas a "dungeon" will block them.