I solved this sorta here: Ignition & Logix Best Practice Tips for better communications - #83 by pturmel
Basically we have a UDT in Ignition that represents the data we want to use. The in the PLC we have a Wrapper AOI that wraps the internal AOI/Instruction/ETC... and maps the data to a PLC UDT that matches the Ignition UDT. Anything that needs to write the PLC side is done via the divert write tag actors in @pturmel toolkit.