From some other posts, it seems that the the BMW factory stator uses wire rated for maximum temperature of 180C and I really don't think this is up to the job.
If you could get your OEM unit rewound with 220C rated wire or perhaps even 240C rated wire I think that would be one good option, but many shops do not have these better grades of wire.
From personal conversations with the engineers at ElectroSport:
I have been told their wire is rated for 220C, and they have done other things to their design to reduce the heat load on the stator.
RM stator ( $99 USD) says they use 200C rated wire, better than stock, but probably not good enough to last "for ever"...
Ricks offers a unit for $165 USD http://ricksmotorsportelectrics.com/
but does not specify the wire insulation rating ...