Proof of concept using Class Table Inheritance

app.rb

require 'sequel'

DB = Sequel.connect 'sqlite://database.db'

class Person < Sequel::Model
  # has age, name, type
end

Person.plugin :class_table_inheritance, key: :type

class Chef < Person
  # has recipes
end

class Scientist < Person
  # has university
end

class Physicist < Scientist
  # has preferred_laser
end

schema.rb

Sequel.migration do
  change do
    create_table :people do
      primary_key :id

      String :name
      String :age

      String :type
    end

    create_table :chefs do
      foreign_key :id, :people
      String :recipes
    end

    create_table :scientists do
      foreign_key :id, :people
      String :university
    end

    create_table :physicists do
      foreign_key :id, :scientists
      String :university
    end
  end
end