Revamp: Koffing -> Weezing

[Black Temple Gaurdian]

To me,
Koffing and Weezing feel very well thought out. They are balls of dense, toxic gases. Naturally they can use gas-based moves. The fact they are gaseous means that they can build static electricity (which causes thunder (and thunderbolts)). Expanding on their highly volatile nature, it makes sense that they can learn explosion and self-destruct, but also some flame-based moves, using the gases like fuel for a flamethrower.
However, to me at least, that does not indicate "It's a flame move, it'd be able to use it" or thinking along those lines. For example, Overload, just where is this sudden internal charge of electricity coming from? For Koffing or Weezing to build up such an intense charge internally, they'd likely to have exploded once or twice at least. Afterburn I'm unsure of, how exactly would Koffing or Weezing produce time-delayed embers? On the one hand passing volatile gases over embers would cuase them to erupt. On the other hand how does that work independantly of the pokemon, and where would the embers come from anyway?

So yes, please please can we have some thought out reasoning behind this, please?

On a more positive note, I agree on Burnout. The more damage it takes the more likely it is to leak said volatile gases, increasing the attack's power.

Edit: Fireball? Seems a pretty obvious one.