The use of a sensor-less system definitely has its appeal to avoid the implementation challenges described above, but tends to have a significantly larger margin of error in terms of inferred vs. actual ethanol content - not great when trying to extract the most safe power out of your engine.
I've had the factory flex fuel logic running on my '18 for ~4 months/4500 miles and roughly 10 fill-ups of varying ethanol content between E10 and E55. I've yet to see a matured ethanol content >4% off from measured via an external continental sensor. Generally takes a single 10 minute highway & city drive to get the ethanol content to mature.
I think there's nothing wrong with utilizing the factory Ford logic, especially considering how many million cars/trucks currently running just fine with it. Even though we're "pushing" the limits with increased output, it should be able to be calibrated correctly with adequate safety margin and significantly improved ease of implementation. The problem will be modifying the Ecoboost strategy to use the "full" Ford flex logic that's in the production flex fuel strategies.
