No ones replied - and, while im not qualified too much to answer....
1. from a storage point of view very simple = just get a MicroSD card of about 16 to 32 and that'll hold everything thats ever been produced on the amiga and then some...
2. Memory, max it out (not sure what the ceiling height is for memory on a 500)
3. CPU: subjective but it would seem people are developing for 68030 onwards??