just 4 possible ways. 1. get a phat psp 2. put a phat mobo in your slim (btw has anyone tried it?)
3. modify the mobo so that you can somehow get it (almost impossible unless you are even smarter than all sony devs) 4. ask sony to do it (its not gonna happen... i know it...or its gonna cost milli0ns of $$$)
so its not possible but the second way is a bit considerable in my point of view but again its gonna need a lot of modding and skill you will need to build the psp all over again and also put the phat components in too(wifi board, powerboard etc)....