base_transaction.rb

module CheetahCub
  class Transaction
    attr_reader :transaction_delegate
    delegate :save, to: :transaction_delegate
    # def save
    #   transaction_delegate.save
    # end
    def initialize
      @transaction_delegate = Config.module_prefix::Transaction.new
    end
  end
end

desired_use_case.rb

require 'cheetah_cub'
CheetahCub::Config.version= "1.1.1"
CheetahCub::Transaction.new.save # => Hello from 1.1.1

CheetahCub::Config.version= "1.1.2"
CheetahCub::Transaction.new.save # => Hello from 1.1.2

gistfile1.rb

module CheetahCub
  module Config
    extend self
    attr_accessor :version

    def url
      ENV["CHEETAH_CUB_API_URL"]
    end

    def module_prefix
      class_eval("CheetahCub::X_#{version.gsub('.','_')}")
    end

    def version= version
      @version = version
    end

    def version
      @version || '1.1.1'
    end
  end
end

x_1_1_1-transaction.rb

module CheetahCub
  module X_1_1_1
    class Transaction
      def save
        puts "Hello from 1.1.1"
      end
    end
  end
end

x_1_1_2-transaction.rb

module CheetahCub
  module X_1_1_2
    class Transaction
      def save
        puts "Hello from 1.1.2"
      end
    end
  end
end