It's already in there -- the Clarity's "HV Charge" mode does the same thing as the Volt's "Mountain Mode" to the best of my knowledge, just at 58% SOC.
I'm looking forward to taking a drive through Monitor Pass (8300 ft) when the air clears up, will do some experiments then too.
The Volt's Mountain Mode or our HV Charge mode should be called "pre mountain mode". They charge the battery. What I am looking for is a mode where you start with a nearly full battery and the car combined steady battery power with engine power. So for example whenever the engine RPM exceeds 4500 rpm start drawing from the battery. The main goal is to increase performance and reduce engine noise in steep section.
I have driven the monitor pass in Clarity with medium+ load. It was very noisy, the car did not perform well. If I do it again I will just keep the battery charge and climb the steep section in EV Sport with some sharp accelerations to keep the engine running.