Did some reading, did some looking, did some more reading, got a migraine.
I tried out all the combinations of all the highway:path-track tags, all the designation:(rights of way) tags and bicycle/foot/horse:yes tags, basically because I wasn’t sure what was doing what. It turns out the issue I was looking at is only on the highway:path tag along the left of bottom row which most people may already know!? (funny appearance where multiple =designated tags are being considered)
So in short: please could someone with mapnik changing powers please take a look at this when they have some time. (specifically:  the bottom row issue with multiple =designated tags co-existing, and  the lack of rendering of ‘designation:x’ tags. This will inevitably lead onto  some change to track rendering, as 2 linear dash lines don’t work well together)
Of the keys/values shown in the image, [designation, highway and x=designated), when rendering designation needs to over rule highway when used, and foot/bicycle/horse:designated need not be considered for rendering at all. (it simple opens up a backdoor way, where there is another solution). highway:track needs to visually co-exist with designation: tags. Only really an issue if highway:track stays as it is, which is currently graphically inconsistent with all the other tags in this set. It far better belongs closer to tags like highway:service than highway:footway. It’s a sizey feature with noticeable width that can bare routes upon it. It’s impact on the environment ranges in subtlety, and is stated in tracktype=. Varied opacity would reflect this well.
I’d happily commit time to doing this, but I just do graphics me. If I just had mapnik working infront of me with an editable rule-sheet maybe I could be of a help, but that’s not the case. I therefore leave this as an attempt at a justified request.
(Just to note that ‘designation:’ is actually still proposed according to the wiki, however it appears in josm and potlatch and is widely used, and it’s a critical step in correct tagging)