To your first point whcih is super valid, I would say instead of them being locked into noob lobbys, the lobbys themselves are elo locked so a new player could in theory play in higher elo lobbys but the color indicator would suggest they are too low to really compete. To your second point, That wouldn't be much of a concern because those returning players won't be in that elo for long, much like any competative game. that actually would allow new players to still see those awesome K-Style moves but not be over run by uneven matchmaking. Then again, from my first suggestion in this reply, that would essentially provide options for low player count as well as a beginners only place to start.
