[Twisted-Python] Twisted app structure

[Simon]

Hi everyone,
I've recently discovered Twisted and am now thinking of shifting my
development from PHP to Python. I'm writing to you to get some input on
how Python and especially Twisted could be used in my development.

The main app I want to build could be described as a dynamic messaging
service system. It will listen for events on different protocols and
react to them according to a service description that is set up for that
event.
A service description will contain a chain of calls to different modules
of the system, for example UserModule->GetUser(event.owner),
MsgStore->Retrieve(event.msgid),
GroupModule->StoreContact(group,msg.sender). 

It seems to me that this system would be suitable to implement in
Twisted. Would you agree?
I also would like to know what you think would be best; building a main
app that handles traffic on all protocols and reacts to it, or building
gateway apps for each protocol that store data in a db which a main app
retrieves and acts on?
Would appreciate any thoughts on this.

Looking forward to hearing from you.
/Simon