In particular I suspect there's very few gains that can be made for wireless communications. My contention is that there exists a information-theoretic lower bound on the amount of energy it takes to transmit a given amount of information a given distance. Like a heat engine, at some point you can no longer make generational improvements in efficiency. You get asymptotically closer to the bound, you can't ever beat it. And wireless power tends to dominate the power budget of anything that uses it.

High-bandwidth signals require more power to travel a given distance, low-bandwidth signals go farther on less power but transmit less information. Intuitively this is why you can go worldwide with CW (Morse code) on just a few watts of power, while a SSB signal on the same frequency doesn't go far at all. But I think you can mathematically support this by playing with the bandwidth+power terms of the Shannon-Hartley theorem.

If we want to transmit a given amount of data per time unit, there are two natural extremes. We can either transmit it at the average data rate necessary, or we can race-to-sleep by blasting it out as fast as possible. I'm not sure which is more efficient given that SNR is inside the log2 of the S-H theorem, it depends on the relationship between SNR and bandwidth as you spread a given quantity of RF power thinner and thinner. Based on the log2 I would think this is an inverse-square kind of thing, making it an equivalent tradeoff.

Showerthoughts: because of the Inverse Square Law, it's probably more efficient to make a mesh of multiple small hops than a single long shot. As the spacing of the mesh decreases to zero, you end up with a wire.

Also, check out the ESP8266 chip, it doesn't have a BTLE onboard but it does handle the "SOC with low-power wifi" thing.