Yes! A religious noble republic! That was what I was attempting to explain in my original post, sorry if I didn't make it clear.
And of course, the Knights were the closest thing to a Christian banker at the times they existed, right? So they could easily adopt some values that seem similar to say, Venice.
Perhaps, instead of continuing to beat on Catholic Lithuania after their victory at Tannenberg, they notice that they are hated by most Catholics, especially Lithuania, so they give up all claims on the Lithuanians, beyond what they already have, along with giving a great deal of money to Poland-Lithuania and focus on fighting the schismatic Russians, rationalizing that it would be safer for them to fight actual heretics, rather then a people who are no longer heathens?
They also note that the Venetian Republic is very close in composition to their own government, and adopt many laws and customs of the Venetians.
They could note the success of the Reformation, and either become Protestant, or realize that they spent the last few centuries murdering until all around them was Catholicism, and that there's no point to converting from a religion that you subjugated entire cultures for, to a new, mostly untested religion.
Sound plausible?