Thanks for you suggestions. For some features such as Default > Count mode this is already possible using expressions in the Arithmetic operator (see attached), but due to the order in which RailClone evaluates events unfortunately it is not possible using Evenly Count mode and for technical reasons would be hard to implement.
I'm also afraid you cannot access the material IDs of the clipping spline, this is by design. Limit by material IDs isn't intended for use with clipping areas and only works with X/Y splines otherwise there may be problems whereby a clipping path may have multiple IDs on the same spline, but also many users use clipping paths in conjunction with X/Y splines that may also use the limit by material IDs option to place segments.
I hope that helps, please let me know if you have further questions.