The three warhead configeration must greatly increase the potential damage area, plus a phalanx gun system will struggle to defeat one never mind three warheads. StarStreak uses a three dart system, why not something bigger?
A high/medium long range UCAV able to remain aloft for extended periods (24+ hours) equipped with a couple of Perseus or equivalents would provide an excellent maritime surveillance/strike platform. With proposed in-service date of 2030 the design must be aimed at as many future manned/unmanned platforms as possible. The more nations baulk at human loss, the more unmanned platforms will do the dirty work, plus you don;t need to worry about planning to recover any downed pilots.
I'm waiting for the first through deck UCAV cruisers to appear, it must only be a matter of time before ship builders capitalise on the cost/space savings (manning for one) of designing a UCAV only mini-carrier, which is able to conduct long range surveillance/strike missions and send real time imagery not just to the parent vessel but to a nations tri-service C&C centre back home. Something the size of a Japanese Hyuga Class with a crew of around 3 to 400 plus six to nine UCAVS.
Over the next twenty years UCAV costs will hopefully decrease as the technology matures allowing for expensive, large and labour intensive strike carriers to become a luxury, not a necessity. A new breed of cheaper 'Kamikaze' UCAV's could even become a reality designed to saturate a fleets defences without incurring excessive loss of life, all sent aloft from a small lean manned platform.
I seriously doubt the UK or other European countries can afford to develop a next generation F35/F22 replacement, they should instead focus on long range less stealthy UCAV's capable of launching extended range stealthy munitions such as Perseus.
