[c-nsp] modifying an aggregate-address advertisement

[Jeff Bacon]

Scenario: 

I'm aggregating my address range to eBGP peer using aggregate-address. However, I'm multi-homed to said peer, and I need to advertise a preference (MED or as-path) to said peer via the multiple paths. 

---------
router bgp 36193
!
address-family ipv4 vrf bats
  neighbor X.Y.Z.A remote-as G
  neighbor 10.196.61.1 activate
  neighbor 10.196.61.1 soft-reconfiguration inbound
  neighbor 10.196.61.1 route-map bgp-outbound-map out
  no synchronization
  aggregate-address A.B.C.D 255.255.255.192 as-set summary-only
 exit-address-family

route-map bgp-outbound-map permit 10
 match ip address prefix-list outbound-pub-prefixes
 set metric 49152
 set as-path prepend last-as 3
-----------

I would think that the route-map should apply to the aggregate summary address - but it doesn't. 

I can influence the metric by setting

--------
  route-map set-unpref-map 
    set metric 49152 
    
  aggregate-address A.B.C.D 255.255.255.192 as-set summary-only attribute-map set-unpref-map

-------

which for the purpose at hand is sufficient, but not all my peers honor MED. 

I can use a null-route plus a network statement, sure, but that is less than ideal for my purposes.

Is there any way to artificially extend an as-path on an aggregate address? 

Thanks,
-bacon