If you want to exclude Gamesparks from being nativized, this should be able to be done by using Exclusive blueprint nativization instead of Inclusive and picking what particular blueprints you want to nativize. Inclusive will include everything that it can.
As for your two proposed ideas, the first would be possible but I wouldn’t know where to start and the exclusive instead of inclusive setting would be much easier. The second, if you could find a way to pause it, may also be possible but reading the code generated by nativization and finding what needs to be removed will also prove more difficult, and you’d have to do this every time you package, adjusting for any edits.