Only two classes are available for 148s - Newcomers championship (JD and JC only) and Pony Show Jumper of the year. (JA)
For Newcomers Championship you must have jumped 4 double clears at first round then be placed first or second at a second round event.
The qualifications for Pony Showjumper are significantly more complex but basically through being placed at earlier rounds or being on the Pony European teams.
Clearly you can't make 2016 as the first round qualifications ended months ago. No harm in dreaming - but a more modest aim might be better?