Here is a wish list for a common !FastSim framework: 

1. (optional, lowest priority) ROOT Independence
   (for example, using some classes from CLHEP and Boost.Python for factories, config. file, etc)

2. (optional) config. file independence (specifying only in-memory representation and access methods)

3. Module factory that creates modules instances at run-time '''by name'''
   
   With ROOT it's just {{{gROOT->GetClass(moduleClassName)->New()}}}

   http://root.cern.ch/root/html/TClass.html
   
   The simplest solution without ROOT would be
{{{
  BaseModuleClass* moduleFactory(string const &name)
  {
    if(name == "Module1")
    {
      return new Module1;
    }
    else if(name == "Module2")
    {
      return new Module2;
    }
    return NULL;
  }
}}}

4. Memory manager that minimizes the amount of memory allocations and
   that creates/destroys/clears all data collections used by other services and modules.
   It also clears all data collections produce by other services and modules between
   events in the event loop.  
   (see ROOT {{{TClonesArray}}}, {{{ExRootFactory}}})
   
   http://root.cern.ch/root/html/TClonesArray.html

   https://server06.fynu.ucl.ac.be/projects/ExRootAnalysis/browser/trunk/ExRootAnalysis/ExRootFactory.h

5. Central configuration manager that stores all parameters for all modules and
   that provides access '''by name''' to these parameters
   ({{{getDouble(name, defaultValue)}}}, {{{getDouble("JetFinder/MinPT", 10.0)}}})

6. Data manager that provides access '''by name''' to all data collections created by other services and modules
   (see {{{fwlite::Handle<T>::getByLabel(event, label)}}} in CMSSW or {{{TFolder}}} in ROOT)

   https://twiki.cern.ch/twiki/bin/view/CMSPublic/WorkBookFWLiteEventLoop

   http://cmssdt.cern.ch/SDT/doxygen/CMSSW_5_3_2/doc/html/d1/dd2/classfwlite_1_1Handle.html

   http://root.cern.ch/download/doc/ROOTUsersGuideHTML/ch10.html
   
7. Universal object that could represent all physics objects (particles, tracks,
   calorimeter towers, jets) with possibility to add user defined information
   (see !FastJet {{{PseudoJet}}} & {{{UserInfoBase}}} classes, CMS PAT {{{UserData}}}, {{{ExRootCandidate}}})
   
   With ROOT, user defined information can be implemented quite easily
{{{
  class ExRootCandidate
  {
  ...
  private:
    map< const TClass*, TObject* > fInfoMap
  };
  
   //------------------------------------------------------------------------------

  TObject *ExRootCandidate::GetInfo(const TClass *cl)
  {
    map<const TClass *, TObject *>::const_iterator it = fInfoMap.find(cl);

    return (it != fInfoMap.end() ? it->second : 0);
  }

  //------------------------------------------------------------------------------

  void ExRootCandidate::SetInfo(TObject *info)
  {
    fInfoMap[info->IsA()] = info;
  }
}}}
   
   https://twiki.cern.ch/twiki/bin/view/CMSPublic/SWGuidePATUserData
   
   http://fastjet.fr/repo/doxygen-3.0.2/classfastjet_1_1PseudoJet.html

   http://fastjet.fr/repo/doxygen-3.0.2/classfastjet_1_1PseudoJet_1_1UserInfoBase.html
   
   https://server06.fynu.ucl.ac.be/projects/ExRootAnalysis/browser/trunk/ExRootAnalysis/ExRootCandidate.h

   http://isscvs.cern.ch/cgi-bin/viewcvs-all.cgi/ORCA/Examples/ExRootAnalysis/UserRootAnalysis.cc?root=orca&view=markup

8. Modules that consume and produce collections of universal objects