Well, it always seemed like it would take someone who’s crazy to bring this all the way to the courts, and Ismaik certainly fits the bill. Even Martin Kind baulked at doing so when push came to shove. There’s been a consensus for some time that 50+1 won’t survive a legal challenge.
The most likely outcome appears to be that money will flow into clubs based in destination cities, so the candidates would probably include Hertha and Union Berlin, HSV and St Pauli, Cologne, either of the Frankfurt clubs (although I've just noticed that FSV have been relegated to the fourth tier), Fortuna Düsseldorf, maybe Stuttgart.
In broad terms, the Bundesliga is almost certainly going to become a lot more like the Premier League, but with better beer, which breaks my heart a little. If people want crass, nouveau riche financial determinism, then the PL already has that covered.
Realistically, there is an alternative here is already somewhat practiced in which large German-based multinational companies are purchasing shares in clubs. Allianz, Adidas and Audi each have minority stakes in Bayern München. Puma has a stake in Dortmund and recently Daimler purchased an interest in Stuttgart. Those make sense and would likely be more palatable for a German audience than having questionable foreign owners who would not have the same attachment and regional self-interest in the club. Some of the teams I think would benefit from what you are proposing are most likely the following:
Eintracht Frankfurt: in my opinion they would easily be the biggest winners of any chances to 50+1. They are the country's banking hub and have a renovated stadium. I've read a few things previously that have suggested there would be a fair bit of interest from the financial community in investing more in the club, so perhaps Stuttgart hold the model for them to use in the interim.
Stuttgart: They have one of the largest fanbases in Germany and are based in one of the country's more prosperous cities with plenty of local research and development and industry. Their stadium is also quite big and was renovated for the World Cup.
HSV: "Der Dino" has been in disarray for years. The city itself has an extremely high employment rate with a commercial sector that is much more diverse than simply its notable port (i.e. banking, aerospace industries) and its also a major media hub in Germany with the likes of Der Spiegel and Die Zeit published in the city. Like with Union Berlin, I could not see St. Pauli selling out their traditions.
Bremen: They had a really good title winning side a few years ago, but have sort of lost the plot in recent years. The city is a hub for manufacturing (Airbus, Mercedes-Benz), breweries (Becks) and is either the German or European headquarters for a number of companies including Kellogg's, Kraft Foods and InBev. Their stadium was also renovated for the World Cup a few years ago.
Hertha Berlin: they are Germany's capital city and have a large historic stadium. However the drawback with Hertha is that Berlin is a government city, which generally lacks an industrial/financial core, due to its Cold War history. Thus, while a large German company like Deutsche Bahn is based in Berlin, it's also state-owned, which makes it unlikely to receive that sort of local corporate interest one would get in Frankfurt or Munich. Union Berlin would be unlikely to receive such benefits, simply because it would take a reversal of the club's current operating stance. Somebody like Dynamo Berlin could be a RB Leipzig type project, but is so politically tainted that it seems unlikely.
Fortuna Düsseldorf: They have a 54,000 seater stadium that is fifteen years old and in located in Germany's telecommunications hub. The conditions are ripe for them to do something. They even have a Japanese version of their website.
