I really don't understand what you're trying to say.
What I'm saying is, this would not work, because there are more than five roles. Any combination of five existing roles can result in a win. Riot would have to do one of several things:
1) Decide which five roles you get to choose from, and ignore the rest. This is dumb, as it excludes champions from selection
2) Decide to combine some roles into a mix role - for instance, you would probably want either Assassin and Top, or Assassin and Mid to be combined. You can't do things like choose Mid then choose AP Carry or Assassin as a sub selection, because then you're forcing mid laners to play a specific role, which is completely unnecessary.
3) Other things, likely.
This is a team game, and you have to spend your time together in queue making decisions that will benefit your team. In blind pick, this is nearly pointless, as you have no idea what you're going up against, so the only things you can do are make sure you have a way to stay in lane, make sure you have varied damage, and make sure you have means to control a fight through other effects - Crowd Control is what comes to mind. The roles and lane assignments you make are far less important than those points, and you can meet those goals through many combinations of standard roles.
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