If no one on your team is familiar with PLC’s, why use one? IMO, your comments indicate you think it is the wrong choice. Are you just looking for validation of your opinion?
PLC comm ports, especially Ethernet, will only handle predefined protocols. Read the product info carefully.
In general, your questions would be far better answered by an Omron product specialist rather than a bunch of random people on an electronics forum on the internet. Sure, some of us are well versed in PLC’s but you’re asking generic questions so you’ll get generic answers like the one above.
Oh, yeah. Forgot to mention that none of your concerns are valid with modern, industrial PLC’s. Arduinos and single board computers aren’t industrial products.