I've read over your suggestions and have the following feedback for your feedback.
Pure oxygen? Yes please. That would likely be a good addition to nerf the Qi' in some way. However, it'd be neat if they could have their own take on a breath mask which wasn't directly a Vox one.
EMP fragility is due to their body being a mass of biological electronic conduits and batteries. Such an influx of energy would stun them, definitely, but it would not cause them to rebound! They have limited control over their energy, not full control.
Regen from energy would likely need nerfs. Honestly, that would be its only purpose. Too much energy will hurt them, too little will hurt them. Just right will keep them stable, a little over the sweet spot will heal passively. See the document. I also agree that somatoray-esque exploits would have to be patched.
Glowing would have to exist to nerf their innate regenerative abilities. It's ample, yes, but their blood *glows.* Hard to make an excuse for why they would be able to control its glow.
They are not energy beings, they're merely biologicals who harness electricity naturally. As such, I'm not changing their blood or limb mechanics. Being attacked and losing blood, however, would drain energy.
Thanks for your suggestions!