Yes it can be done but it still could be a while before DLM relents and releases the banding.
You can't use homeplugs to replace the cw1308 cable. They can only be used for ethernet.
You could locate the router downstairs by the master socket & then use the homeplugs to run ethernet upstairs though.
The cw1308 cable from the filtered side of the master socket downstairs should connect directly to the router upstairs not another filtered faceplate.