From a designer's point of view, the first question when I sit down to design something is not the specifics how it will work but why something like this would be fun and also what exactly would be the cool thing about it. What makes it worth playing? What is the design goal? Only then, it makes sense to develop a system that highlights the strengths of that game aspect. Otherwise, there is no common base to argument from and the whole design process might remain a matter of taste.
That's the difference between "There should be a differently colored arrow when I nearly finished the race" and "The game gives no feedback about how close I am to the goal. That kind of feedback would increase the game experience in the same way as it does in f.e. shooters: When you kill an enemy, it is announced and shown, how close you are to winning/losing"

I consider the (combo) magic system as one of the extras introduced during the Clonk shareware series that are on the same level as constructing castles, doing alchemy, researching, farworld's hunting and decomposing of animals, freezing and hunger in farworlds and many more. Instead of asking ourselves which system we are going to reimplement and which not, we should, in my opinion, see the game mechanics introduced in C4-CR as ideas ('Anregungen') and examples we can analyse to find new ideas for game mechanics that will coin OpenClonk in the future. Of course, I am not saying that we shouldn't consider reimplementing a particular system just because it was in CE, but we shouldn't also reimplement it just because it was in CE.

I am writing this because I have doubts about a reimplementation of a magic system. If I didn't know the combo magic system from CE, it would sound like a very specific feature to me. A feature that actually drills right through the current concept of controls, tools and menus - implementation-wise but also as a game mechanic.