What is it that has made the system so widely used these days? My parents imply that when we used the system (admittedly back in around 2009), we were the only ones using it on most rides, and they said that we stood out so much that a lot of guests in the regular queue gave my parents and me very judgmental looks as we got onto rides. Nowadays, however, a great number of people seem to use RAP. Admittedly, things such as inclusion of those with SEN needs and disabilities, as well as knowledge about disabilities, has improved over the last decade, which would naturally lead to an increase, however I can't think of a reason why use would have increased so exponentially over the last decade.
In fairness to Merlin/Alton, they need to be inclusive to those with disabilities in this day and age, and I think it's really good that they are being so inclusive. Also, I'm not really sure how they can solve the issue. The only plausible way I can think of is through a virtual queueing system, sort of like what Universal does with Jimmy Fallon & Volcano Bay.