middleware architecture for data collection

I am attempting to use integrator to assimilate a custom ERP system with 
Mapics.  Here is what I am pondering currently:

I want to use an integrator object to define custom parameters for MO operation 
shop activity.  This would be the primary data entered by production techs and 
I want it to be available even when the system is down for maintenance.

Here are some questions about a possible approach:

It seems clear that some sort of middleware would be required to cache 
transactions.  In a recent visit Phil Joseph mentioned that integrator does, or 
may soon support postgresql on linux.  Is it feasible to build integrator 
objects on postgresql that are available when the iseries isn't?  How would 
authentication work in that environment?

What is the best approach to push shop activity to PM&C?  Our current data 
collection user profiles use a program called amjpca.  Is this what we would 
continue use?  How could I maximize the amount of data validation and editing 
that Mapics does (versus custom logic) while accomplishing this goal?

I know this is a big question.  Please don't feel you need to swallow the whole 
elephant.  If you have any relevant information for me please respond even if 
it is not an answer to all of my questions.

Thanks in advance for any and all help.

Josh Diggs
California Fine Wire