I thought that by now UEFA would have established a competition for former succesful clubs, who didn't qualify for any other UEFA competions any given season. So similar type of competition than in South America, Copa Sudamerica, Copa Mercosur and its' other predecessors.
Call it Greats League, for example.
I'm pretty sure it would attract good TV and sponsor income, and since these would be big / traditional clubs, match attendance would be good too. Next season's competition could include clubs like Manchester United, AC Milan, Dortmund, Marseille, Sevilla, Tottenham etc.
Depending on how many teams UEFA would want to take part (perhaps 8, maybe 16) the qualifying criteria could be:
1st catergory of eligible clubs:
- former CL winners during the past 30 years
2nd catergory of eligible clubs:
- former Europa League winners during the past 30 years
- former Conference League/other UEFA competion winners during the past 30 years
3rd catergory of eligible clubs:
- former CL finalists during the past 30 years
- former Europa League finalists during the past 30 years
- former Conference League/other UEFA competion finalists during the past 30 years
4th catergory of eligible clubs:
-former CL winners more than 30 years ago
-former Europa League winners more than 30 years ago
-former Conference League/other UEFA competion winners more than 30 years ago
5th catergory of eligible clubs:
-league winners of TOP5 leagues
-league winners of TOP10 leagues
etc.
Within categories, clubs could be ranked with recency, so more recent winner/finalist would be ranked higher.
To ensury that there wouldn't be low standard participants, teams could be required to play at top tier (or at second tier) in their domestic league. Might also make sense to limit number of participating teams from the same country.
I'd like to see this type of competiton, participants would likely vary quite a bit from one season to another, although some clubs might be there for several years in a row,