1.It couldn't make them automatic championship team. Contenders I guess, but it also depends who are these 6men. Teams like Barca or Panathinaikos would take down those random 6men teams. Europe is no China.
2. "signing-NBA player limit" rule would not be introduced. Every league has different foreign players rules or limits. But best teams play in several competitions and has absolute freedom in market. Like in Soccer, there is no cap spaces or smth. rich teams dominates.
And Euroleague is just a international competition. It's not even a real league, it just selects best European teams from different leagues and thats it. It can't limit any signings, because afterall, it's not even their teams...