getting back to Flitwick...he was a dueling champion so he is a capable wizard. He could be in the Order, it just never says. all because Flitwick isn't like Dumbledore or Hagrid, doesn't mean anything. it just means that they could win...but it also takes swiftness and ability to trick even the smartest people...like Snape when he fool the Dark Lord/Dumbledore, or when Quirrel tricked Dumbledore. they weren't physically strong, but had enough to trick the two most smartest wizard's. so you can't really cross off Flitwick yet...look at Ginny. she isn't physically strong as the others but she has mean hexes.