Inventing a GPS waypoint for a DP?

The ODP out of MMK for runway 36 reads, "climbing left turn to 1800 via
325° bearing from MMK NDB before proceeding on course".

It seems to me that the easiest way to fly that with a GPS would be to
create a user waypoint which is a 325 bearing, 20 (or whatever) mile
offset from MMK NDB and insert that into your flight plan before the
first real waypoint in your clearance. Take off, track to the user
waypoint until reaching 1800, then do "direct" to the next waypoint.
Can anybody think of a good reason not to do it that way?