Problem being: Which war?
The TYW did not have clear-cut alliances, the enemies of the Emperor
changed and sometimes even fought against each other.
So you might want to specify _when_ and against _whom_ (and _how_/_why_).
E.g. the war would have been finished if it was only for the Bohemian-Palatine
rebellion, and if Denmark would not have tried to benefit from it.
That would be an early victory, with little deep consequences,
most questions still wide open.
A victory after 1628 would virtually imply that the Emperor and the Catholic League
are able to make their main goal come true, namely the restitution of all clergical
possessions in Protestant hands since after 1555.
This is very unlikely, and needs a very profound derivation.
Actually I am writing a timeline where the Emperor gains a somewhat improved
situation by letting go his most ambitious goal:
The Two Golden Lions.