I'm not sure about the offset on the banshee rims but I know the lug pattern is different... You can purchase banshee hubs and install them on the blaster (spline count and diameter is the same) if you want to run the banshee rims...
Let me let everyone in on a little secret (not that it's a huge secret but I'm banking on the fact that I'm the only one crazy enough to try it). You do not need a banshee axle to widen the rear and you don't have to go with crazy spacer studs... The blaster shares it's 4/100 rear lug pattern with only one other ATV... the 250 Tri-Z. Only difference is, rims made to fit the Tri-Z have a "wider" offset (to the tune of 4" total width on the quad).