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Use case: I want to show that a way is closed for access. For this, I would like to display an icon near the start and the end of the way, and maybe a few icons along the way itself.
ASCII art (X=icon):
The difference to a ShieldSymbolizer is that ideally the icons along the way would be placed at 1/2 of the way, then at 1/4 and 3/4 etc. until they are too dense.
For very short ways, a single icon at 1/2 of the way would be best.
(Come to think of it, this behavior would make sense as being the default for the ShieldSymbolizer.)
#2338 addresses the start/end ability.