Ok, so i have received the Digi One IAP 
Great little device with one DB9 RS232 port, and one terminal block with RS232/485. (Two ports can be used simultaniously.)
An added bonus is the device can be powered over ethernet (PoE).
Setting the network settings was a breeze once i had downloaded the Digi tool for this (no CD included).
The web interface is quite clumsy and unorganized (so are the manuals), but that beeing said, it allows for a wast amount of custom configuration and possibilites.
Using an integrated wizard in the web interface i configured one DF1 master on port 2 (DB9), and enabled incoming AB-ethernet, Ethernet/IP and modbus.
I ordered mini-din connectors to make the serial cable myself, but it turns out the Micrologix connector is non-standard proprietary coding. The standard mini-din can be filed to fit, but it will fit very loosely. I ended up using the original 1761-cbl-pm02 cable.
Once i had all the configuration in the web interface correct (made some mistakes on the first try), Ignition connected with no problem using EIP protocol.
Auto-discovery of the PLC files also works, although symbol names will not show as they are not stored in the MicroLogix CPU.
If i disconnect the serial cable, but leave ethernet plugged in, Ignition wil show an error in the tag status and connection status as “disconnected” (correct behaviour).
I am also able to connect via RSLinx / RsLogix simultaniously (you have to use AB ethernet driver in RSLinx for this to work).
All in all, a pretty much painless experience 