Take a good quality fixed/fixed hub. You've got your track cog+lockring on one side and a freewheel threaded onto the other. All's fine and dandy, but then ... you take the bike offroad (let's say either xc or cx). Is this a recipe for disaster, or have others run this setup without issue? Do any hub manufactures even warranty such an odd setup? I'm trying to plan for maximum versatility, but this may be pushing it too far.