Vin Rouge
I see no reason why standard diesel fuel could not be used the Diamond DA42 is certified for use with both Jet A-1 and standard diesel motor fuel as it is more or less the same thing.
Having done the manufactures maintainence course on the engine I was told that Jet A-1 has far less lubricating qualitys and so the challenge was to get a Diesel engine fuel control system to run reliably on Jet A-1, this is a problem you would not have in reverse.
Added to this the life expectancy of a Harrier in a pan European conflict would probably render long term reliability a non issue.