I'd love to have a one fits all battery.
I sort of wish it worked that way, too. -- But, the best advice is to think about your protected batts as the 'primary' batts for your flashlight and your IMR's as the primary batts for your REO. If you need to carry spare batts for both devices, make the spares the IMRs because they'll drive your flashlight just fine (shorter run time than the specific batt you mentioned, but drive it just fine) and are also the appropriate cells for your REO.
And this is indeed the approach I take:
The battery in my flashlights right now: Work truck light has an older AW 2600 mah (panny cells) protected. The battery in my personal carry light right now is a much newer 3400 mah AW (panny cells) protected. Both the tool box on the work truck and the tool box on my personal truck have a couple of 2000 mah AW IMR. -- The "spare" batts are perfectly appropriate for the flashlights (shorter run time but perfectly capable and safe), and good enough to do the job for the REO if I'm caught out unexpectedly for an extra day somewhere. If I was running super-sub-ohm (like .3 or something), I'd probably choose different "spares".... If all I used 18650s for was the REO, all I would own would be my favorite IMRs. If all I used 18650s for was my flashlights, all I'd own is AW protected.