FRR allows to use route-map for aggregate-address
! router bgp 65002 neighbor 192.0.2.1 remote-as 65001 ! address-family ipv4 unicast aggregate-address 203.0.113.0/24 route-map FOO redistribute connected exit-address-family !
Add this feature to VyOS
Proposed syntax for CLI
set protocols bgp 65002 address-family ipv4-unicast aggregate-address 203.0.113.0/24 route-map XXX