You said you don't want to make a Hollow partly because it's expensive, right? I have something that might help with that and make it more interesting...

You're the Summer Queen; you have a court now. Get them to make it with you, and make it open to anyone in your court, as a symbol of the bond that now ties you all together.

If you want to take things further, you could probably even put a few doctors/healers there, and open it up to any Changeling in need, to symbolize your duty to protect all, regardless of Court, and craft a pledge that calling on such aid would bind them to, holding them to the rules of the Hollow until such time as they leave.