If anything, installing GrapheneOS on a Pixel probably reduces the risk of something happening to your phone, that’s kind of the point with having an Android distribution that maximizes security and privacy.
And because the installer is so simple that you just connect your phone, open a browser and hit three buttons, it’s really unlikely that you’ll accidentally brick your phone trying to install it.
Hosting data yourself wouldn’t be required, but it would become an option.
You’d have the option of leaving your identity on your home server, or a separate domain/website, or host your data and identity but use another instance to federate.
Though, designing UX for this will be an interesting challenge.