Stew,
You got me thinking about this again...
After a google search, I found a few who said they added a priming circuit, backfeeding with no issues. Looking at the service manual at the link above, it looks like it will only backfeed and energize the coil, would need someone smarter than me to confirm.
At the following link, here is a unique solution (wire diagram included), where they add the prime circuit inside at the remote panel. A simple solution, but not without risk, as the author states "don't press the prime button and start button at the same time..." :)
http://www.gmccoop.com/onan_prime_circuit.htm