Bullet loan to avoid bad KFW interest rate?

Here is a thought experiment. We will use the full loan amount in the KFW 153 program for two residential units. That makes 240,000€ loan volume. The rest through a normal annuity. To achieve an affordable rate with KFW, longer terms at the current 0.95% interest are necessary. On the open market, we have offers at 0.5%, so significantly better. What do you think about choosing the bullet repayment option at 1.0% with the minimum term of 4 years? Then the whole thing could be secured soon after with a forward loan. Depending on how long you stay “cool,” you can probably get quite a bit out of it? Do banks perhaps even do that at the initial closing if the remaining amount over the KFW loan is also taken out at the same time? Really annoying that the repayment bonus is still tied to a loan until July.