Wow
Just wow
Way to prove you do not understand the subject
Serial hybrid
it will never have less power until the battery runs out of juice
not for a second
bigger ICE engine will do precisely nothing
Nothing
Software is king
Put it in 'I am towing a trailer up a mountain' mode so it does not let the battery fall below, say 40 percent, [rather than 5 percent of a tiny I3 battery] and how long of a sustained incline before the battery fails to power the vehicle?
That is your design parameter
https://trucksontriangles.com/steep-grades/
CA I80 5-7 max grade for 40 miles.
worst I could find