This would be way to powerful even with the cap issue aside.
Fire already has immolate to provide heavy burst fire quanta production.
I like the effect, I just don't think the fire element needs any more help in this particular area.
This spell would do the most good in an element that currently lacks quanta production boosts... like
,
,
, or
As for the quanta cap issue. I do have to agree with Elbirn here. There was a time when there were no caps whatsoever. People complained incesantly that fire bolt rush was WAY too powerful. And they did have a point since spell damage has so few counters.
These caps are in place precisely to prevent bolt rush abuse. ESPECIALLY for the fire element.
Adding the drop to zero at the end of turn will help deal with Farenheit abuse, but bolt abuse will still be a balance issue.
If enough cards introduced to mitigate spell damage then maybe this will change. For now, though, I don't think buffing firebolts is a good idea.
... On the other hand, this could be very interesting if you allow it to produce quanta for other elements, and more importatnly, if you were to restrict it from being spent on spells... I think you might have something then.