BabaJ

Unfortunately none of this presents the artist with a clean UI with exposed parameters or ‘overrideable’ parameters. Is there any plan to improve the material override parameter workflow for solaris ?

Don't see what you mean by that - especially jsmacks suggestion - everything is laid out at the top level of the node - what is it you feel needs improving?

Is there a plan or even just a way right now to override a parameter value from a shader, but just for a single primitive?

You can either set shader parm values in a wrangle prior to importing the geo to Lops, or while in Lops use a Sop Modify node (setting on Unpack USD Primitives to Polygons - or use unpack USD Primitives to Polygon node inside Sop Modify node) - then use a wrangle there.

Your probably wanting:

?