The way I see it, if there is a lack of skilled UK airsoft design and manufacture, that's an opportunity... It will be a niche area, but as with most anything, skill and quality are valuable commodities that people will pay for.
One of the things worth thinking about is the various rings that make up Airsoft. Guns and RIF aren't the whole hog.
Design a better lasting battery, not only might airsoft appreciate it, Apple might be buying your patent.
And then there is the mask/goggle system... Nobody to date has developed a goggle system with an inbuilt HUD and software allowing proper force command, blue on blue detection etc in Airsoft and Paintball.
The military are trying of course, things like the Q-Warrior. And some CoD fans tried to get a smartphone based App allowing you to play airsoft just like a game. But anybody who designs this for airsoft and pb will really have something the monied of the sports might shell out for eh... Not to mention the potential real world buyers (like army and police forces etc).
But these are mere brain farts.
Get trained in as many skillz that will keep you employed as you can. If you try to make it in airsoft and fail, you still need to make the rent.