How to dynamically select rails views for specific model instances (ie. a specific user)

application_controller.rb

#An overly complex example of dynamically micro-managing which templates are shown..
class ApplicationController < ActionController::Base
  
  # In this example we assume a using Devise so user_signed_in? and current_user are provided.
  # Note: the value returned here could very well be a user's uuid if you needed to provide
  # one specific different view for a single or small collection of specific users.
  # @returns String || nil
  def get_custom_view_name
    #This doesn't need to be lazy, but it can be.
		@custom_view_name ||= begin
			if user_signed_in?
				current_user.custom_view_name				
			end
		end
	end

protected
  
  # This will add a view lookup path based on a User's theme_name attribute, however
  # if this theme does not exist thats ok too, we will still look in the conventional directory
  def customize_view_templates
		custom_view_path = "app/views/custom/#{get_custom_view_name}"
		prepend_view_path( custom_view_path )
	end

end

show.htm.erb

# /app/views/widgets/show.html.erb
# The default view we show to most users.
# NOTE: gist.github.com does not allow multiple files with the same name so I changed its extension, however,
#       in your application this would have the same name and extension as the custom version.

<h1>I am an everyday widget</h1>

show.html.erb

# /app/views/custom/razzledazzle/widgets/show.html.erb
# The custom view we show to users where current_user.custom_view_name == 'razzledazzle'

<h1>Hello <%= current_user.name %>, I am a customized widget just for you (and maybe your friends)</h1>

widgets_controller.rb

class WidgetsController < ApplicationController

  # Allows us to make custom client views in /app/views/custom/#{custom_view_name}/api/v1/widgets/show
	before_action :customize_view_templates, :only => [:show]

end

The benefit here is that I wanted to avoid doing something like

if current_user.custom_view_name.blank?
  render
else
  render( :template => "app/views/custom/#{current_user. custom_view_name}"/controller/action)
end

Which would need to exist in some form in every action that could be overwritten; and I felt was less maintainable.