Modularization of a Rails application?

For a client I have to present options for "modularizing" a Rails application. By "modularization" is meant that the application allows to plug/unplug (install/uninstall) whole vertical slices of functionality including models, views, controllers, routes, migrations.

I know that this is not the most recommended approach in Rails.

I have seen both Engines [1] and Hydra [2] which seem to solve a problem like this at different levels.

Are there any other (even if experimental) approaches to this? Also, are there reviews or success stories about using these approaches for the said purpose?

I have also read John W. Long's article "Better Modularization for Rails 2.0" [3] and the discussion on the Rails core mailinglist that it spun off [4].

Does anybody know if there are efforts to realize some of the stuff discussed there?

Thanks!

[1] http://rails-engines.org/
[2] http://blog.nicksieger.com/articles/2007/10/06/railsconf-europe-hydra
[3] http://wiseheartdesign.com/2007/6/15/better-modularization-for-rails-2-0/
[4] http://groups.google.com/group/rubyonrails-core/browse_thread/thread/45685895778b1357/

Not being very helpful here, but I recently looked into this issue as
well and did not found a satisfactory approach. There very much
_should_ be a better approach, I agree with John in [3]