"once you account for electricity BTUs being more productive than coal BTUs (easier to use precisely) then the "unknowns" drop out of the relationship"

First, I'd note that Hirsch is talking about oil: his hypothesis is that GDP will drop in a 1:1 relationship with oil, as oil declines. The summary of the paper quoted above suggests that Cleveland is talking about the relationship of GDP to all fuels, which is very different. That approach suggests that wind, solar and nuclear (or, god forbid, coal) electricity will substitute for oil quite nicely.

2nd, The paper says: "If we are to sustain current levels of economic growth and productivity as minimum long-run goals, alternative fuel technologies with EROI ratios comparable to petroleum today must be developed, or there must be unprecedented improvements in the efficiency with which we use fuel to produce economic output".

Well, we've done that. Wind, solar and nuclear combined with PHEV/EVs fits the first requirement (alternative fuel technologies with EROI ratios comparable to petroleum today), and the improvements in efficiency are being found.

3rd, this paper is from 1984 (so the data is 25-35 years old), well before it was clear that since that time US (and world) GDP would grow much more quickly than it's energy consumption (even including electricity). The best example of this is California, which has kept per capita electricity consumption flat over the last 25 years, while growing it's GDP relatively quickly.

4th, Ayres used "exergy services", which are not "very close to BTU parity". Exergy services are work performed. So, for instance, a Prius performs the same work as a similar vehicle with half the MPG, but uses half the BTU's. Strictly speaking, a Prius can perform the same work as a Hummer (transporting people), and use 20% of the BTU's. An EV also does the same work as a Hummer, and uses about 1/3 of the BTU's as the Prius, and 1/15 of the Hummer's...and so on.

Please note, this has been revised several times.