Actually I think the original idea of Razor of the Dawn Castle is a good location, and could be made to work well, if there was some Imperial reason that it suddenly needed to transform from lazy backwater border keep into a major venue to hold a Winter Court (say in two years time).
The first thing that comes to mind would be a major Shadowlands power rising that needs to be handled diplomatically rather than via the usual Crab show of force (think a new, sudden Fae Kingdom or some such that has made Alliance overtures with the Imperial Throne to help them fight some OTHER threat from the Shadowlands).
Then you'd have the PCs be envoy's from their respective Clans all racing to mini-empire build what the Clans need for the Court and to impress/ally/dominate the new Faction.