class CustomBase(object):
    # Generate __tablename__ automatically
    @declared_attr
    def __tablename__(cls):
        return cls.__name__.lower()

    # Every class has an id field, by default Integer
    @declared_attr
    def id(cls):
        for base in cls.__mro__[1:-1]:
            if getattr(base, '__table__', None) is not None:
                type = ForeignKey(base.id)
                break
        else:
            type = Integer

        return Column(type, primary_key=True)

Base = declarative_base(cls=CustomBase)