I'm not sure that pilot licenses have any equivalence with educational qualifications. Amongst other things qualifications, once gained, remain in place where as pilot licences require currency. I think a nearer equivalence would be professional registrations.
I'm a lapsed PPL/IMC, but my professional post-nominals are "MSc C.Eng MIET". The "MSc" is my most senior "qualification", the "C.Eng" is my professional registration (Chartered Engineer) and the "MIET" is the membership status of the professional institution which polices my behaviour and currency.
I could be a C.Eng without any degrees (it's more difficulty, but it can be done) and having the degrees is not enough to get C.Eng accreditation. To get the C.Eng accreditation you need to demonstrate a certain minimum level of "underpinning knowledge and understanding" (aka "UK&U" - for Chartered level the level is the equivalent of a Masters and an Honours in engineering disciplines). You then have to demonstrate a history in which you have exhibited five "competencies" (Theory of engineering, application of theory to real problems, management & leadership, communication and professional behaviour). These are assessed by assertion, reference and interview. If you are passed through this process then you must continue to show compliance with the codes of conduct and also undertake a minimum of 30 hours "continuing professional development" per year to maintain the registration.
Now I haven't seen anything in the process of getting to ATPL that has equivalence to an academic qualification, but I *can* see an equivalence to a professional registration. You have the three elements - a minimum level of "UK&U" (aerodynamics, air law, meteorology, navigation theory etc etc), a history of demonstrating the required competencies and a requirement for continuing development/training to remain current. As others have said, the required academic level of the UK&U is sub-A-level (in British terms), so I suspect the level of equivalence wouldn't be at Chartered level except for those pilots who DO have higher degrees, but I could support an argument for Equivalence with Incorporated Engineer.
Of course there would need to be a suitable Institute to assess, award and police these registrations for this idea to have any mileage.