Using our Advanced Rules feature, you can allow certain orders to be submitted as returns, although they are past the timeframe. How? We've got you covered here:
Following these few steps, you should have this configured in no time:
Set the general return timeframe to the maximum days (or a large value, e.g. 999). This can be done in Return Settings -> General.
Create a rule with the highest priority (1) that is checking for the order tag. This rule needs to "Allow Returns".
Create a second rule with a lower priority (2) named "Days since delivery date is more than x", x being the number of days for matching your standard return policy. This rule will not Allow Returns.
Voila. In no time, you'll have this all set up on your portal. Advanced Rules can do miracles it seems.