So I started working…
I’m still not quite sure what my game will be like, but I’ve decided to keep it simple and do something where you move a player through a 2D environment. That requires levels, ideally a level editor (it probably takes less time to code that than to manually create the levels?) and some kind of physics engine. I don’t have any physics in my Renaissance engine yet. So I started from scratch after all, using SFML and Box2D.
So far I’ve compiled Box2D (I’m always surprised when that works flawlessly on Windows), created a basic high-level architecture/hierarchy for the game objects/levels (keeping (de)serialization in mind for level editing/saving/loading), created an SFML window which can handle being resized and wrote a debug display class for the physics – I figured that’d help me debug physics better, but it’s basically not very important… I don’t even have physical objects at this point! (Besides some test objects to debug the debug drawing…)

I have no game, but I've proven that Box2D is indeed a physics engine.
Well, I suppose that’s just me doing the easy things first. And I fear I might end up having a nice level editor but no game to go with it. Oh well, we’ll see.