You cannot blackmail your players into paying an extravagant amount for more content. It's not going to happen. People support active projects. All you're going to see from this is people pulling their support, not you gaining more. I've enjoyed your VN, I love the story and the style of it. But, setting a price tag on your work to your players is absurd. You are a crowd funded game, an independent developer, and no one is under any obligation to support you. Holding your work hostage has no merit and will only hurt yourself.
You are still getting content as a patron. UHA is being worked on, made by the same people so you will get the same or better art style and writing since people improve skills over time. Oath Of loyalty stands on it's own as a complete experience with multiple endings. Most developers would have abandoned the game at version 0.3 if it even got past 0.1
It is like a movie studio that will do different movies and if one is a hit, then they work on the sequel. If not they work on a different movie franchise. Maybe the first movie will gain cult status as time passes and then may be worthy of a sequel later on, in which case, the studio return to that.
It is not holding anyone hostage, it is trying efforts into something else to see what works better. Just like nobody is obligated to support a project, nobody is obligated to work nearly for free. To put it in perspective Let's say the game is worked on for 90 hours a month for each person, the money coming in is 500 a month and there are 2 people working on the project. Split, that is about $2.70 an hour which is not even half the Federal minimum wage, even if it were just one developer it would barely be half that minimum wage, this is far from an extravagant amount. All this doesn't even count the cost for electricity for rendering, assets for 3d models and whatever hardware cost in case of hardware failure.
The goal being asked would amount to 11 dollars an hour which is still near minimum wage in most states.
It is not like the sequel is done and the developers are holding the game hostage. You are asking the developers to put another year of their time to work almost for free to work on a sequel.
Despite all that, Oath of loyalty has been worked on for over a year for way less than 300 a month according to Graphteon for most of that time. In the end it was still completed and wasn't abandoned.
So the choice for the developers is to work on a sequel and get the same results if the goal isn't met or try different things that until they get a better results. Each project is more than a year of effort trying to complete the game and not abandon it. Another year of time spent on a project that could be used for anything else.