I'd like to make a custom domain (pick-list) for a feature service that is a view. Will this corrupt the parent service?
The short answer is "no", you cannot edit a view in that way. You can try, but you'll notice the option isn't even available to you.
Hosted View Layer:
Source Layer:
If you attempt to manually edit the service definition on the view, you'll get an error message that what you're attempting isn't possible on a layer view.