I did. On a Lakland 55-01 from MK1s to Nordstrand Fat Stacks. I completely removed the circuit as well, leaving it as a passive bass. The result "for me" was perfect. But you have to keep in mind several factors:
1) Do "you" (not your teacher or anyone else) have a problem with MK1s. If so, what is it? What would you be looking for if you upgrade?
2) MK1 is sort of P-pickup in a soapbar shape. Are you looking for a similar sound, or a J-type sound or a humbucker sound?
3) Many also reported good results keeping MK1 pickups but replacing the active circuit only (to Bartolini NTMB or Aguilar OBP-3).
4) There is no drop-in replacement from Nordstrand for 4-string MK1 pickups. It will be a custom order.
5) Then there is the problem of selecting which Nordstrand model. Big Singles? Big Splits? Fat Stacks? Duals Coil wired for series? Dual Coils wired for parallel?
6) Don't forget that there is a drop-in replacement from Bartolini.
I recommend bestbassgear.com for your pickups purchases.
Here are some clips I recorded with my (now gone) 55-01:
1) Stock MK1:
http://mp3space.com/file/82519/5501-mk1
2) Fat Stacks both in stacked mode:
http://mp3space.com/file/82517/5501-fs-stacked
3) Fat Stacks both in single-coil mode:
http://mp3space.com/file/82516/5501-fs-single
I repeated the same boring line twice then again up one octave. First part is neck only, second part both pickups, third part bridge only.