Secret room is on page 178 of the new edition of Mage the Awakening, and stated it can increase the space of a room:
the subject space’s volume is increased or decreased a number of steps along the Area Scale factor table equal to the spell’s Potency.
Now I don't see why this would be not be allowed, but I'm sure other spells that increase/provide merit dots explicitly mention it.
It seems like this could replace some versions of merits (like sanctum) that track location size, if this spell were made lasting.
Likewise demenses that can either be acquired by merits or in game effort are related to size. Are they effected?
Does casting and extending this spell to lasting provide or interact with the various versions of safe space merits in any way?