Kings_Kid sent a good question via site mail. Your clones do NOT need to come from the "seven year" bubble.
The bubble is there to try and keep some diversity in the teams.
Clones from other teams may be from teams in the bubble.(Example: You have 1927 Yankees. Some one could choose 1931 Yankees as there "laboratory" and have a 1927 Lou Gehrig clone on his team.
Players are NOT exclusive, now. Just teams inside their "seven year" bubble.