OK, more information coming in: the new Mini ML will not be a big change (apart from the supported types of wire) and the Yihi rep didn't recommend it as an upgrade for current owners of the Mini M. They will however come with a totally new double 18650 device that should target the DNA200 market coming Xmas.
The more I think about it - given the range of wattages that you vape with - the more I suspect you do need a double 18650 device.