My last stop planned is Luxembourg, so Switzerland is definitely the closest option. I'd love to ski somewhere like Verbier or Zermatt, but I'm worried it'll be difficult to find accommodation for a reasonable price (by swiss standards) at this point.
I wouldn't mind traveling to somewhere like Poland or Slovenia for much better value, but all their resorts look like they're at much lower elevation.
FaunaSkisWhere will you be on the continent for christmas? It's pretty easy to travel around without flights because there are no hard borders and trains all over central Europe but you should pick somewhere close to where you're going to be so you don't lose whole days of travelling.
Your best bet for Early Jan is to stick to the resorts that start higher up as they're considered 'snow sure' (or as much as you can be with the changing climate) and there are options in most countries with terrain in the Alps.