What about something groovy like one of these? It has probably been on one of those fantastical "reality" renovating TV shows, but just such a funky option for a low ceiling - or as a wall feature :) I think Beacon and/or About Space had a variation recently??

Kind of like painting your carpet with big spots. FUN!

The CCTV solution is nice technological fix but why not avoid the inevitable issue of your box gutter failing and redesign the roof? Without having the plans, elevations and levels I would suggest that falling the roof away from the viewer in your image would allow you to collect the roof water on the (western??) side. There are ways to hide a gutter without hiding it inside your building and I personally think that one or two elegantly detailed downpipes can add to the quality of a building, why hide the obvious need to get water off a roof? Also, I would be very surprised if your architect doesn't already have a solution to this, it is a basic requirement of design.

Re-did fly around model to correctly show rear decking and landscape idea, We have are about to start ground works