ASA 5525 Two Outside Interfaces on Same Subnet

[CiscoMedMed]

I have a long established ASA with one 1Gbps interface on the outside. There are many NATs and ACLs associated
with that interface so I don't want to touch it. But I have more Azure ASR and backup traffic that I want to get to the 
edge switches without clogging the pipe for other production traffic. The idea would be to use route maps such that
if traffic comes from specific IP it NATs and egresses Gig2. But all other traffic would egress Gig0 as at present and 
all inbound traffic would come to Gig0 as at present. 

What would I need to make this work and be 110% certain nothing is disturbed that currently passes Gig0/OUTSIDE?

interface GigabitEthernet0
 nameif Outside
 security-level 0
 ip address 1.1.1.1 255.255.255.0

interface GigabitEthernet2
nameif Outside2
 security-level 0
 ip address 1.1.1.2 255.255.255.0

interface Port-Channel1
 nameif Inside
 security-level 100
 ip address 192.x.x.x 255.255.255.0

[Rob Ingram · Accepted solution]

@CiscoMedMed you cannot assign an IP address from the same subnet to 2 separate interfaces. It would error when you applied the configuration. You'd need an IP address from a different subnet.

If you don't want to "clog up" an interface you could configuration another port channel with 2 outside interface (but same IP address)....but there's not much point if traffic egresses the same ISP connection.