Dynamic ValueTable Columns in Python Toolbox

[RandalGreene3]

As per the Limitations section of https://esri.jiveon.com/docs/DOC-3210 and the ideas of https://geonet.esri.com/ideas/6812, I would like to see Python Toolboxes (and even Script Tools and ModelBuilder Tools for that matter) be able to have dynamic values in ValueTable Columns, so that each row can have a different picklist of values for the same column.

[RandalGreene3]

Another limitation is when the primary column in the ValueTable is of parameter data type GPLayer (for instance if you want the user to be able add raster and/or vector datasets), then browsing to disk (as opposed to picking a layer already added to the map) only lets you select *.lyr files!