That's fantastic! I've been trying to package as many apps as I can as flatpak (because flatpak rocks, fight me), I will definitely look into winepak to package Windows-only software. The fact that it uses a standard and common-place technology, it just needs more exposure IMO. This is the first time I have heard of it.
EDIT: nevermind...
$ flatpak remote-add --if-not-exists winepak https://dl.winepak.org/repo/winepak.flatpakrepo
error: Signature made Fri 20 Jul 2018 03:30:34 BST using RSA key ID A959831C080B608F
BAD signature from " <julian@richen.io>"
Key expired Tue 09 Jun 2020 19:16:34 BST