I dont think a simultaneous store'n'burn would work, since it may lead to positive-feedback: you store the power you gain from store'n'burn in the thing you burn, increasing the output, increasing the input, ad infinitum. Or at least there has to be a barrier somewhere, so that power can leak or be blocked.
Can you even invest in an ingested metal?
If I have ingested a mind and some raw metal, can I sense the difference between them?
Do I have control over what bits of metal I burn? what bits of metal I store in? (I think you can draw from a particular mind at once?)
So what happens if I have ingested some metal and an empty mind: I chose to burn the raw stuff, and store the power in the mind. That's pretty standard so far...
So now I only have an empty mind, and maybe (probably) too much control burning: I burn one side of the metal mind and store it. I believe the power in a mind is akin to fluid in a container? That would mean I start getting the extra power from store'n'burn and storing that atop my own capacity (unless I can multi task, but that leads to possible perpetual 'motion', if tuned correctly)
Same again, but
I guess some of the ideas discussed need a significant concentration and control, and maybe even super-local temporal enhancement...if thats even possible >.>