Well, you can do it right now with firejail. Start with the default config, it prevents access to many sensitive files; then either add more sensitive locations

Well, you can do it right now with firejail. Start with the default config, it prevents access to many sensitive files; then either add more sensitive locations to blacklist, or blacklist your whole home directory and whitelist whatever is necessary. I don't recall the exact configuration format, but it's something really simple, like whitelist ~/src/*