Hi Paul,
In a pretty similar situation to yourself regarding breaking into the HA arena- just about to go on C-Bus courses so will let you know. Spoke for hours to the fantastic people at the C-Bus shop about my intentions, growth markets, prices, technology etc - very knowledgeable.
My understanding of the lighting configurations is as follows ( sure it will be corrected by the pro's if wrong !)
It's the usual price V flexibility equation - every light with it's own module and ID will give you maximum flexibility for lighting mood settings etc, but it will also cost the most. Talk with the client and get a 'lighting map' so you can understand what he wants to achieve - with this, you may be able to 'gang' up lights to provide the required settings - but be careful of loadings especially when dimming.
The 'limit' fuses are usually on the output side and are to protect the modules as these aren't cheap and are generally of a much smaller value than the normal 6A lighting MCB ( 1A,2A,3A) In this configuration each output wire has the neutral tied back to a common bar and the phase goes from each fuse to the appropriate light.
Hope this helps,
Regards,
Paul.