FWIW using std::variant (or whatever is your in-house variant) to store message types is very common. Also in well designed low level binary protocols message

FWIW using std::variant (or whatever is your in-house variant) to store message types is very common. Also in well designed low level binary protocols message types have a discriminant header already so often common to wrap them in an ad hoc-variant which doesn't have a separate discriminant.