There seems to be a bug in VyOS 1.2.2 and 1.2.3-epa1 where you can't set "remove-private-as" because VyOS somehow thinks you are setting up an iBGP session. This bug can be reproduced with a very simple configuration:
set protocols bgp 1000 neighbor 10.0.0.1 remote-as 2000 set protocols bgp 1000 neighbor 10.0.0.1 address-family ipv4-unicast remove-private-as
When you try to commit these commands, you get:
[ protocols bgp 1000 neighbor 10.0.0.1 address-family ipv4-unicast remove-private-as ] you can't set remove-private-as for an ibgp peer [[protocols bgp 1000]] failed
It won't even work if you configure a specific local AS for this neighbor:
set protocols bgp 1000 neighbor 10.0.0.1 local-as 1000
If you need more information, let me know.