Cool! It is a good workaround to store point/vertex attributes data until we have the proper attributes support. You can use the three available UV maps in Octane to store up to two float values in each one, and later use the UVW projection node to get these values for shading.
obviously not limited to color, alpha also works and any attribute. I guess only limited by the number of uv sets that octane can read. good enough for now, relieved that I can do this project in octane and not mantra