Yesterday, I, finally managed to complete an outline-sketch of the functional working of the mail-remote plugin glue code. After a couple of hours sleep and a good lunch, got NotZed on the evolution channel asking for his views about the outline-sketch.
He was ok with the approach that was taken in the outline-sketch, however, wanted to refine and trim some of the functions/assumptions. He explained me the facts about the data that are passed from the mail-remote plugin (server interface). Also, he suggested few things like defining structures for the interface types exposed in the IDL file and emitting individual signals for each type of "change_type" instead of a single signal with multi-parameters.
As a matter of fact, the values that are passed to the callbacks, registered in the glue-code to handle signals from the plugin, assumes a particular order and the same should be maintained.
So, with those suggestions, the mere outline-sketch has transformed into a more-or-less neat sketch that clearly defines the shape of the glue-code. (Now the sketch spans to multiple-files.)