If all packages have the All Package Servers assingment, then the new PS will get all the packages.
The best way to do this is to copy the Packages directory from a PS that has all the packages, remove the xml files, install the psa on the new ps and then stop the sma service, replace its Packages folder with the one you copied, start the sma service, and then run the ps event scheduled task (full name elludes me at the mo) on the smp say 30 mins later ir you can wait until it is triggered sonetime in the early hours.