Not a bad list of destinations... Internaut, it's at times like these you need to be spoilt in a place that's relatively easy to get to.
Berlin offers the Regent Schlosshotel (a former Ritz Carlton). It's barely 20 mins in a cab from TXL in a very smart part of the city. The place is so fantastic you need never step foot outside, apart from when it comes to time to leave - why they even have a bath butler!!!
Alternatively, try flying to ZRH and driving across the border into Bavaria. There's a few smart spa hotels about an hour's drive away and the sweeping views are stunning.
If you're planning to venture further afield, it's probably worth waiting for the next batch of I fares, though I suspect we won't see any more of these until late January. There's nothing like an All Day Deli bag to take the shine off a weekend getaway.