PS: Is CartoCSS already in use?
CartoCSS is used for the web rendering, while MapCSS is used for JOSM. The split is unfortunate, but maintaining our own rendering stack that understands MapCSS will not work because of too few developers. We did this for some years, but at the end the development of the stack just halted because everyone has more important things to do.
PPS: How to proceed with ETCS markers as they should(?) be equal in europe but have different names due to different operating countries?
We use the same markers for multiple countries already:
https://github.com/OpenRailwayMap/OpenRailwayMap-CartoCSS/blob/master/ signals.mss#L660