Why not have an airsoft license, similar to a driving one. All held on a national database, and the license can be revoked. Must be over 18 to hold one, and no purchase of RIF allowed without it. Players will have to sit a theory test on VCRA, UKARA, safe handling, correct terminology, battery storage, etc. And a practical exam to demonstate proper use of eye-pro, magazine and battery changes, safety procedure before entering the Safe Zone, etc. Their Airsoft license can be checked at sites to make sure the player is legal to carry a RIF.
And a provisional license for under 18s, to make sure they are responsible enough to be allowed to use a two-tone gun.
Could also introduce gun registration numbers. Every gun has a unique index number, held on a national database, and when you sell a gun you complete the details of old owner and new owner and send them off to the Airsoft Licensing Agency (could be located in Swansea for example). This would also mean stolen or lost guns could be traced back to the owner.
Note: Yes, it is April 1st. And this is not a serious post.