The usual way to handle this transition:
  1. Add the new Investment accounts to the existing pool to handle the new brokerage statements/investments
  2. Use the Disbursements line in each of the reconciliations to move the money from the closing investment to the new investment.
If the transfer did not completely occur in the period for both sides of the transfer:
  1. Enter a journal entry that both debits and credits the pool for the amount of the transfer
  2. In FACTS, change the confirm date on the side of the transaction that did not clear during the period to the following period.

Once the old investments are finally closed, you can enter closed dates in the investment accounts so they won't need reconciliation in the future.  The dates should be entered on the Investment Account record as of the closing date of the cycle and this should be done before starting the next cycle.