I've long thought that it'd be really good to have more control over which splines a generator acts on.
At present we can limit by Spline Material ID. However can not limit by ranges yet, that'd be nice to have. (So Spline Mat IDs 1 to 10).
Additionally I think it'd be really useful to be able to limit by the length of the spline. Quite often when a spline is very short very different logic can be required to handle those situations well, and to be able to hide that all behind the generator would be really nice.