I know spiked flats is a legit mtb/downhill thing. I always think though the first time there is an incident where those meet the shins, some spd's would start looking reallllly good.
Ask me how I know....
Also, could always take a pedal wrench with you and your pedals. We have Cycleops 400 pro's at our work gym with a combo of SPD and toe strap. Guys still swap them out for their SPD SL's or Looks then swap back when done.
FWIW, try the GCN show youtube workout videos. They have both spin class and mountain climbing videos.