This won't work. S2 and S1 chips are not intercompatible, and can not even run the same protocol stacks:
S1 = Freescale chip - 802.15.4, DigiMesh 2.4 only
S2, S2B, S2C = Ember variants - ZigBee, Smart Energy only
Any one protocol stack listed above is compatible ONLY with itself, none of the others. ZB to ZB, 802.15.4 to 802.15.4, etc.
As far as conversion goes, some 802.15.4 S1 modules can be converted to DigiMesh 2.4 but not others. Guidance can be found here for which modules will support the DM conversion: