For a FWD vehicle like ProMaster, I'd prefer an inline engine, preferably with a heavy duty design that includes at least an iron block for durability. And if we want both fuel economy and torque, then it's gotta have low displacement with turbocharging.
Working backwards that would put a new comparable engine around 2.5L in size, with turbo, that can make 250 HP and at least 300 lb-ft of torque, enough to match or beat diesel performance. The engine would be a little smaller than Ford's 2.7L EcoBoost in size, but preferably inline.
By downsizing to equal power, fuel economy differences (MPGs) should be limited to between 20 and 40 percent. The engine would cost less than diesel, weigh less, and should be quieter. Such a comparison would make it harder to justify a diesel.
It should be noted that many large cities in Europe are looking at phasing out diesels in order to improve air quality. When I was in London two years ago the smell of Diesel engines was horrible. I know they are cleaner now, but what do they really bring to the table that a turbo gasoline engine can't, except a little higher efficiency?
There is a recent study about London, if ones looks at data and what many newspapers write, than will find that what is written is not always supported by scientific data.
For example: central London, NOx road traffic sources:
diesel vans: 5%
private and hire diesel cars: 2.9%
Public buses: 14.2%
Heavy goods vehicles: 8%
Taxis: 7%
And that data included all vehicles, not only the most modern ones.
For Euro 6 diesel recent publication shows, even accounting regeneration, that many times the particle matter levels are lower than the air ingested by the engine.
Pollution is real, but sources are many and newer cars are not the only source.
Some notes:
- in most european capitals, excluding London, most buses use natural gas in their modified diesel engines, not diesel fuel (they emit also less noise)
- France their nuclear plants are producing too low electricity => not earning enough money to cover costs.
- There is worldwide a overproduction of gasoline.
Link to the study about London:
http://www.ippr.org/files/publicati...air-pollution-crisis-Nov2016.pdf?noredirect=1
And there are some innovative conversions that would fit even better into our roomy PM's. 
