I'm still not positive I follow you.
I assume that all the internet traffic will come in on the border router. The VPN will terminate at eth0/0 and the client ASA traffic needs to reach the ASA external interface.
If this is correct, then what you need is to put only two public ip addresses one for the SSG and one for the ASA. The ASA will still have a default route to your border router. There is no need to route the ASA traffic through another address on your SSG, just publish it directly to the border router. In fact, running through the SSG will likely create issues with policies and the connections.
For these types of setups I would usually create a three port vlan on the local switch
port 1 border router
port 2 SSG eth0/0
port 3 ASA eth0/0
If you want to use SSG interfaces instead then you can use the bgroup function to create a two port switch.
Create bgroup1 with eth0/0 and eth0/3 as members
Put your public address for the SSG on this bgroup1 interface and assign to the untrust zone
Connect the border router to eth0/0 and the ASA to eth0/3 and they will both see the inbound traffic.