I'd like terrain accurate placement of shards, like having fire near a volcano, but I don't know about actually having the terrain type generate mana. That seems like more work than it's worth, especially since you can terraform. You'd lose a target for attacking, an objective to guard, all kinds of wonderful things. In return, you'd get a complex mechanic that added detail to simple actions. You plant grass in the sand, and your earth mana does... Where would you even get air from, everywhere?
The complexity haters will probably flip their lids over it, and I don't see the same kind of returns that come from a complex resource system in general, or itemized unit construction.
I'm going to wait until someone actually tells us something regarding the design of your initial character before jumping to the conclusion that life and death coming from channelers means channelers are primarily or entirely generating life and death.