There are multiple parts to this, but they are connected..
1) With the advent of LED lighting 15 amps is overkill for a dedicated light circuit. A 16 AWG 300-ft-max circuit could be run off a 3A breaker. That would permit 36 x 10 watt lights.
2) Are there any designated lamp sockets that only LED lamps could fit. eg E4, GU 7.5 or whatever. This would make ceiling insulation less of a problem.