I'm assuming you are not live on PD. If you are live on PD you simply cannot do a full refresh. A full refresh is the safest way pre-go-live. But if you can't wait and you are functional continue on. If you are not functional then work with a super user and continue (if you dare):
Your concern regarding the AID is the key here but there are other concerns. If you know for sure there has not been any activity in PD for a company you should be able to delete all the accounts for this company within the F0901 application. The application will prevent you from deleting accounts with transactions.
Export to a spreadsheet from PY all the accounts from the one company. You do not want the AID field in the export. Then import all the accounts into PD. New AIDs will be created. Voila! The other concerns you may need to address: AAI, DMAAI, AP Bank Account which uses AID, hard-coded reports, model journal entries (F0911), allocations, Fixed Asset depreciation defaults, and there may be a few others. I believe the F0901 application will not delete an account if there are F0911 model journal entries. I don't remember.
Now what happens if you are able to delete all accounts in PD except a few? Then leave them and import all the accounts from PY except these. You then may still need to make adjustments. What if some of these "undeleted" accounts are now different? There are ways around this. If you get to this point let me know.
