I see your point, staying in Grasshopper is a choice. I don’t know a components thats allows what you want. It doesn’t seem to complex to develop, but seems not to be developed (Rich Graph Mapper is an extension of Graph Mapper that could perphas be extended by the author).
If you want to use a Graph Mapper you could do that (position continuity)
graph mapper, same value on 0 and 1.gh (8 KB)
My curves is in 3d, you’ll have to bake it to use it.
curve as graph mapper.gh (7.3 KB)