Ah yes, thanks for refreshing my memory!
It's possible that the fusion bath is enough to trigger the "antimatter generation" that you mention? Certainly the link between dilithium and antimatter is evident from The Alternative Factor
, although what that link is was of course never clearly defined. Also, if the crystals are really able to generate "free" antimatter in this way, it is in effect a shortcut to limitless energy. And while the Enterprise does "as we know from various episodes) regenerate its own power, this seems like a bit of an easy fix. Or maybe not, I may be missing something here!
What I find particularly appealing about Robert_Comsol
's latest notion is that it more easily bridges the gap between TOS and later incarnations of Trek. While your explanation of "different timelines" is one way to explain the differences in the use of of your dilithium setup and the one on TNG, the holy grail would have to be finding one constant technological inerpretation that spans the different series and movies.
I do think that the popular TNG setup (matter at the top, antimatter at the bottom, anihilation takes place via a crystal in the centre) is probably a gross simplification of what actually occurs - and luckily, no onscreen dialogue ever says otherwise. So, what else could be happenning then? A miniaturised version of the TOS dilithium assembly is an attractive possiblity, at least.