Look at what could be, HAS been, done.
 

Just talked to a Honda Insight owner, 60-70MPG hwy, 10.1 gallon tank gets him from Tacoma to SFO.

Just points out the advantages of more closely matching base/static engine HP/torque to actual useage.

And yes, the insight has no "gumption", but that could be easily corrected via the use of a variable volume/displacement/speed(***) SuperCharger. No boost for hwy cruising, just for acceleration.

PSD, Power Split device, for driving/controlling the SC speed. Primary input to the PSD would be the ICE. The "secondary" (low power), opposition or additive input, would be from a permanent magnet rotor A/C synchronous motor itself energized by a variable frequency inverter

Re: Look at what could be, HAS been, done.
 

I think you may have posted this under the wrong forum. Your post is way too generic to be Ford Escape Hybrid specific.