Okay, so building up on the feedback given on the previous item on that topic (thanks everyone, and xiaokj, Alfman and Brendan in particular!), I have tried to improve the design of my daemon and service model a bit further. Here is the new version, feel free to study and discuss it!
Singularity, the Microsoft research OS, implements some very interesting IPC constructs, perhaps more strict than you are looking for, but there might be some good ideas there to be borrowed.