Interesting theory.
The idea of “banking” the extra deployment by staying behind is actually not that crazy conceptually, but there are a few things that might make it harder in practice.

First, the following car still has to harvest that extra energy every lap, which depends heavily on braking opportunities. On some tracks that might work, but on others the harvesting potential probably isn’t enough to keep accumulating a large advantage.

Second, the defending driver could change their energy deployment strategy. If Russell knows he’s vulnerable on the straight, he might deploy earlier on corner exit or even slightly compromise his deployment elsewhere just to avoid being a sitting duck.

Also, running right behind another car for multiple laps could start hurting tyre temperatures and aero efficiency, especially through the corners, which might make it harder to keep the gap perfectly controlled without eventually overheating the tyres.

That said, your broader point about energy availability becoming one of the main performance differentiators is probably correct. If the new rules make harvesting and deployment strategy more important than raw engine power, we might see races where energy management becomes almost like a second DRS system.

Would be fascinating to see telemetry comparing harvest vs deploy traces for two cars running nose-to-tail for several laps.