There's no automated mechanism, but here's a manual technique you could try:
  1. At the start of the summer, reduce the payment and change the interest calc type on the account to be interest-only (via Tool #20 Update Account Information).
  2. Use Tool #51 Miscellaneous Loan Maintenance > Payment changes to schedule a payment change for the normal payment to resume in September.
  3. Create tracker reminders to monitor and perform maintenance on these accounts each year.
We would of course recommend appropriate disclosures for the member to explain how this would affect the member's normal monthly payment and expected payoff arrangements.