I'm not sure what a DL ombudsman is going to be able to do that AF can't handle already. The joint venture has been in place for a long time, AF and DL routinely handle issues for each other. OP got the seats he thought he was supposed to get, everything worked out. What is going to be improved by inserting another person into the mix?
Are you
kidding? 
If I address AF employees in my three-semesters-in-Phonetique-a-la-Sorbonne+SciencePo French, sure, they'll snap to attention and do somethign if I tell them how. Absolutely. There's a cultural heirachy here, after all, and I might complain to Macron over cocktails at Brasserie Lipp. after all.
If I tend towards a provincial accent much less English? Good luck getting any response at all other than "Delta handles that" or "use the app."
On this one: my position is, Delta needs to step in, demand control, and force the AF socialists to do something.
Weet u niet?