As you know, src_ip has the IP address and src_nt_host captures the host name. In your case, if your src_ip doesn't have the value (i.e. IP address) you need, and if that's present in src_nt_host, you can alias it and it should work.
Alternatively, if you go down the approach of props/transforms (as above), as soon as the first src_ip is obtained, the transform will return. So, if Source_Network_Address_as_src_ip returns a value of src_ip, your IpAddress_as_src_ip may not run or overwrite it. Please check/test it once.
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