I would be inclined to use a Spline if you want to add the shape in the sketch and a Fill or Boundary Surface if you want to add it in the solid or surface model. I'm not sure how well they will behave if your change your model parameters a lot.
F. R wrote:
At the moment i have to construct a tangent curve with the "Equation Driven Curve" tool, but this is not very flexible for parametric designs.
What is reasonable manufacturing tolerance for this feature?
Looks to me like a couple of tangent arc curves well within any reasonable manufacturing tolerance could be used to replace the complex curve.