One argument against pro/rel in US soccer is that “rel” would scare away owners who have been bought a team in the top league.
Yet, I’ve never heard thoughts from the actual owners about this.
My guess is that owners are not nearly as concerned with pro/rel as critics of pro/rel say they are.
How do I know?
Because there are many pro/rel leagues around the world and they don’t have trouble finding owners. Some of those owners are even American who also own teams in non-pro/rel leagues.
American Stan Kroenke, for example, owns teams in the non-pro/rel MLS (Colorado Rapids) and pro/rel English Premier League (EPL) (Arsenal).
American-owned Fenway Sports Group owns a team in a non-pro/rel league MLB (Boston Red Sox) and pro/rel EPL (Liverpool).
As does the American Glazer family who own a team in a non-pro/rel league NFL (Tampa Bay Buccaneers) and pro/rel EPL (Manchester United).