The UM2 dual extrusion is dead... long live the UM2 dual extrusion!
This might be a solution for the tinkerers among you:
What is needed for the dual extrusion?
A complete UM2 hotend -> available in the UM store
A Bowden tube -> available in the UM store (officially for the UMO, but it seems to work for the UM2 as well)
A Feeder including the motor -> currently not available in the UM store but the specs are available on Github; and there are alternative feeder designs... means: print it.
a new firmware: download it at Github, set EXTRUDERS to 2 and compile it!
So except the feeder parts everything is available. And for the missing parts, it might be worth watching the spare parts section of the UM store for the time coming... (you know, some little birds tweet also during the winter... )
However, this would bring the difficulties with it that UM was facing when they started with the UM2 dual extrusion. But remember that dual prints with PLA were actually not a problem...(check the forum, there was an information some time ago about this). And PVA can be printed at even lower temperatures...