"the fact the UK-DUS leg is being operated by a leisure orientated airline may put off some business passengers."
Germanwings is not at all leisure orientated. With the exception of onward flights from DUS to Chicago and New York (& FRA and MUC if anyone did that rather than the direct one) everything will be Germanwings to/from DUS by autumn.
https://www.germanwings.com/de/Flugi...erflugplan.htm
As of autumn, the LH product (with the exception of those two longhaul routes ex DUS) will only be available to/from FRA/MUC (for any market, not only the Uk market).