CharlieDontSurff...
I think if you have aspirations in safety and investigation now is a good time to start building upon your operational flying experience. However for a role in an organisation like AAIB you would be need to be a specialist in operations, training, engineering, human factors, psychology, medicine, etc,.
There are a number of things you could do in parallel to you flying career so you can expand on your knowledge, and read all the current and historic accident reports.
PM me if you want further information.
If you want inspiration, read up on Chesley Burnett "Sully" Sullenberger III in wikipedia, in terms of the additional qualification he gained in addition to his ATPL and flying experience.