If you think about why BGR didn't have any major updates for over a year, you can put a lot of the blame on Nutaku...
In the end, it boiled down to money for the following reasons:
1. Low player count - BGR wasn't the easiest game to get into. It had long story scenes (2minutes+ per scene, up to 15 minutes of just reading for the 6 scenes). There was a significant learning curve. Less players = less potential people who would pay.
2. Generous - It was easy picking up exclusive and platinum tickets. At one point, you could pick up a platinum ticket every 3 days just for logging in. Free tickets = no one makes in game purchases. Not only that, you would piss players off if you take them away.
3. Content - The next event in the game happened to involve loli versions of several key characters. Seeing how Nutaku had a loli-ban at the time, they weren't going to go ahead with that event. And by the time the loli-ban got lifted, Nutaku was already busy with other titles.
4. Resources - There were other DMM games running. Translators weren't an infinite resource. And if each new character means an extra half an hour of content for 2 new characters per event, it can be kind of costly if the translators take 10 times as long to convert the moonrunes to English.
So. In the end, because Nutaku barely made any money in the first 3 months, they just quit before they did anything. Hence a long period of nothing happening. But they had so much time before the license expired that they could have TRIED something.
1. If they took a slight loss and burst released a bunch of character content, the generous nature of the game would have solved itself as the players used whatever tickets they had in storage. Afterwards, just continue hosting exclusive characters and the players would have to fork over the dough. Long periods of time with nothing happening means players just build up wealth and you dig yourself further in a hole.
2. If the content was questionable, hop over it like they did in Aigis with Elyse.
3. If you're lacking resources, then those 5-6 DMM games that shut down should have had translators freed up. Considering every other game on the site doesn't need a translator since they're already in English, try using these guys more.
4. Even though the game had a learning curve, it had an all-world chat. Keep the content fresh and new faces would keep showing up and a veteran would definitely help them along.
The game was a good game. Many players think that it is well made. But no, the idea of putting more money into a game that hadn't left the ground the moment it was released was too unpalatable for Nutaku. So they just let it linger to earn passive income until the license ran out.
Basically, your Nutaku as a mall example is flawed. Aside from being told where they can operate and having customers provided by the malls, shops are expected to be completely self-sufficient.
That's not the case here. Certain shops need additional resources from Nutaku, so Nutaku ends up being more like a franchise (corporate actually but that's way too high-level a concept) headquarters who's responsible for dictating how a shop under it will run. It's not like the shop has its own translators and programmers, they were all provided by HQ. And HQ has those specialists working on other games too. If headquarters doesn't give a shop the resources it needs to survive and expand, then HQ is the one to blame when the shop is forced to shutter its doors because no one is going in. The only failing of the game was that it didn't attract a massive playerbase the instant it was released.