Design guidance for for Plug-in/Engine based application

Hello,

Is the following app suitable to a Plug-in based app architecture? I
have been researching this for some time and have not found a clear-cut
perspective to date. I did receive some generous feedback from a post
on Railsforum suggesting an Engines-based approach, so now I am trying
to further explore that approach. All thoughts are appreciated.

App outline:

  1. 5 module complex work flow system to assist in automobile design:

module 1 - spaceframe,
module 2 - drivetrain,
module 3 - aerodynamics,
module 4 - environmentals,
module 5 - controls

  1. Each of these modules are fairly complex and should themselves be
    implemented as n-step wizards

  2. The modules can either be used in sequence to complete an end-to-end
    design project (XYZ Concept Car), or they can be used independently to
    assist in the design of a single subsystem or multiple independent
    subsystems. i.e., a project can encompass one or more modules

  3. Some modules will produce data that other modules can use to complete
    their particular function (for example: controls module needs to know
    about drive train and environmentals)

  4. A user can have many projects (i.e., a portfolio)

Questions:

  1. Is an app like this best suited to an Engines/Plug-in or conventional
    app architecture?

  2. What’s the best way to organize such an application?

1 app?
5 independent Rails applications orchestrated by a sixth app?
1 app with 5 plug-ins?,
…?

Thoughts? Thx,

Dondi.