It will be a big mast just inside 25 miles but at least 15 miles (I think) away from the airport.
There is further terrian protection outside the tolerance of the approach and if there was something to potentially hit the GA would take you above MSA.
I suspect you find a few approaches like this on the Norwegien Coast with high Mountians to the East but the airport on flat land or an island. All the procedures will have you out over water and they will have a direct arrival which will keep you high until the IAF but once past that the MSA locally drops to below the headline MSA.
That said there is nothing stopping you climbing to MSA as long as you have told the procedural controller before starting the procedure that thats what your doing in the event of missed approach.
Some airports depict this situation with a circle inside the normal 25 mile circle with a reduced MSA in the middle inside 15 DME.