Given those parameters, ICE would very likely be on top. For the Fords I compared, there was very little to no difference between the EPA highway ratings for the Hybrid and ICE models. BEVs would be last by a country mile due to the inconvenience and peace of mind factors. EREVs could be at or near the top, but it depends on how they're executed--if they're done like @fordmantpw suggested and designed to keep the engine in its most efficient range, they should lose less efficiency than HEVs or PHEVs at highway speed because they'll just be running more, not working harder, considering that their ICEs are just running as generators, not providing propulsive power.
An EREV adds yet another power train choice for consumers to choose from. Having multiple options is good but it is getting more complicated for the non-enthusiast.
For the case of highway driving on longer trips (e.g. family vacation, snowbird destination travel etc) and given the current state of charging infrastructure and battery technology I would rate the different power train options in this order (best to worst) based on convenience and peace of mind:
HEV
PHEV
ICE
BEV
EREV
Am I close or way out in left field? The issue becomes a lot more complicated with many more variable for city/local driving.
I'm not normally a jeep person, the wrangler looks like a tractor, and drives even worse than one. But I'm digging this. It's incredibly sleek and eye catching. That sloped roofline might not be very practical, but I'll forgive it due to how cool it looks. That feature with the air bridge rear spoiler looks like something you'd see on a concept, that would get canned for production, very bold choice.
If I was ever in the market to buy a jeep, this would probably be it.
The problem with this whole segment is that its large-scale adoption is being driven by gov't regulation, not the market itself. If there's consumer demand, you can figure out what they want, and a large scale manufacturer (like Ford) can leverage its size and capabilities to make what meets the demand. For a segment like this, where it's really a niche market that's being forced into wide adoption by outside forces, how do you figure out what meets that need?
In my case, I'm not parking where I have access to charging every day, but that doesn't mean I never park where I can charge. F'rinstance, my car is frequently parked at my brother's house on the weekends, so I can charge there, and with a 150mi range, I could drive my daily commute all week without burning any gasoline.
I can remember 5-8 years ago I think, Ford was working on a reciprocating engine to be a range extender for the F150. Can't find anything on that though. It was similar to a hydraulic piston going back and forth.