A simple - yet perhaps expensive option would be to have limited cockpit overviews on the IFE system.
United I believe have a channel called "Live from the Cockpit", or something similar. I don't know of other carriers who do.
Emirates are one carrier (there are others) who have cameras fitted to the exterior of their 777's. This can be viewed (in rather poor quality albeit) on the personal IFE screens at every seat.
Both of the above would be a nice interesting touch for enthusiasts on flights, especially the cockpit channel. (Obviously it does not include chatter between the two pilots. That would be fun.)
The only problem is that the most exciting time of any fligh is during take off, and approach for landing etc. At these points in the flight, the crew have already collected the head-sets for safety reasons!!!!
Still, its better than nothing.