This is the route I would take:
1) JAA PPL, make sure that 5 hours of your PPL covers the night qual (perfectly legal hardly antone does it)
2) Get FAA PPL based on JAA PPL
3) Get JAA Multi
4) Get FAA multi added to your FAA PPL based on JAA multi
5) Get FAA IR (you can get an IMC based on that added to your JAA PPL)
6) Get FAA Commercial and transfer FAA Multi and IR to it
Congrats... at this point you are an FAA CPL/Multi/IR
7) Do the 14 ATPL exams
8) Do the JAA CPL conversion (from FAA)
9) Do the 15 hours IR hours required to convert you FAA IR to JAA IR
Congrats you are an FAA/CPL/IR and JAA fATPL