My brother is actually snowboarding in Stubai (outside of Innsbruck) as we speak. Probably very close to where you are going.
As he flew to AMS for a conference first, his routing is no use. He ended up flying to Munich and getting a train to Innsbruck. I've also done that same journey by train, so was painless.
Perhaps you may look at either:
QF to FRA and Eurail to Innsbruck
QF to FRA, then FRA/VIE, then Eurail to Innsbruck
QF to FRA, then FRA/MUC, then Eurail to Innsbruck
The first one is the longest Eurail sector, thus the longest time spent getting there (unless transit at FRA makes 2 and 3 longer). Personally, I'd go number 3 (but that's because I have friends in MUC and can speak enough of the language to get by).