...of established teams, on several levels of leagues.
Not to mention that there is virtually no interest in international European leagues, unless they replace the top national league as in some smaller countries.
I understand this view point if one looks at the current European layout. What is missed in this perspective is that major cities such as London, Paris, and Milan have tremendous potential as a market for a premium hockey league. A city does not have to be a traditional "hockey hotbed" to offer significant market potential from a media/ticket sales perspective. Just look at the NHL's rise in popularity and market-value by focusing on large markets in the USA.
Yes, Stockholm, Helsinki, and Prague would be great markets in this type of league but so would Copenhagen and Vienna. , Cologne and Munich, possibly among a few other German cities, would be elevated as well into the top tier league.
A team in Stockholm for example would likely be better off as a "new" team and not AIK or Djurgarden for the very provincial reasons that exist in those national leagues and to not disrupt those traditional leagues; just like Jokerit leaving for the KHL years ago; but in this case it would be aligned with the NHL.
The point is to replicate the NHL style of play as an "AHL level" league but hosted in Europe; the players wouldn't just be country-specific although that would have some benefits for ticket sales it wouldn't be "forced" on the teams. Perhaps the European teams would even have some shared affiliation with NHL teams to be a finishing school for their players to be closer to their homes.