Setting BGP Aggregator Attribute in Filters

Hi, I have a question regarding BIRD. Is it possible to set the BGP aggregator attribute for a prefix using filters? This would be useful in our anycast setup, where it can be difficult to determine the origin of a prefix. Using communities is unfortunately not a viable option for us — some of our hardware does not support extended communities, and upstream networks often filter them. To clarify, I am not looking for route aggregation itself, but specifically a way to set the aggregator attribute. Thank you for any insights. Best regards, Pavel Trefny