Something similar as with Vyatta Gateway is their possible to have the transit Vlan on VM.
You can not create transit vlan on virtual server as you do with vyatta gateway, because a Network Gateway is sized to handle the routing load for multiple VLANs and the virtual server no.
For more information you can review these documents:
https://www.ibm.com/cloud/virtual-servers
https://knowledgelayer.softlayer.com/topic/gateways
https://knowledgelayer.softlayer.com/learning/network-gateway-devices-vyatta