My first choice for this application would be a Red Lion DataStation Plus.
In particular I love that you can create an application in Crimson 3.0 for the G306 and emulate it on your PC, then convert the project to a DSP and run it there (they don't directly emulate the DataStation Plus).
If you find yourself doing 3rd party to A-B interfaces often, and you can justify a small budget expense, just buy a DataStation Plus.
Red Lion actually sent me one about 8 years ago as a thank you for solving a different problem for them, and I still use it for prototyping. I bought a dozen just like it last year because that's the unit I already had, and because the customer had a 36-hour window for assuring them I had tested a prototype.
Get the DSPLE version at least; it has the embedded "virtual HMI" which is super convenient for troubleshooting.
If you can swing a couple hundred more bucks, get the new generation high-performance DA30D unit so you can try out any of the sophisticated OPC-UA, IIoT, or SQL features, and you have the convenience of USB host and SD cards on a modern small-footprint platform.