Hi,
Thanks for the questions.
You're right, the existing tint operations always overwrite any preceding effects. This can be fixed but it requires some changes to the effects code. In the attached examples you can generally do this by changing the tintstrength line to retain any existing tints. For example, the line below was adjusted by adding the text marked in Bold.
real tintStrength = max(easein(length(v),tintFalloff,0,0,1), fpItem.tintColor.x*RetainExistingTint);
RetainExistingTint is a new parameter I've added to the effect that allows you to include any existing colour effects on a scale from 0 (ignore previous effects) to 1 (include previous effects at 100% strength)
Please see the attached file to see it in action. We will adjust the included effects to include this attribute in future.
Regarding road verges, you might find this tutorial of interest
The only difference now is that I'd probably use Forest Sets to share the splines and surfaces between all the different FP objects.
I hope that helps, please let me know if you have any further questions.
Cheers!
Paul