Commentaries would be great if you could find an anime historian who knows the series well. The commentaries by published kaiju experts that were included on the Classic Media Godzilla DVDs were among the best features on those releases. In fact, I would hold up those DVDs as a generally great example of a release tailored for the enthusiast.
As for interviews, hopefully enough time has passed for people involved in the production to be honest about it. I've noticed that Japanese film/anime crew in particular tend to talk about their work in vague generalities, never getting to the nitty gritty. I don't know if that's a cultural thing or if their employers are strangling the opinions they're allowed to voice publicly. The Alien Anthology set is a great example of a collection of interviews that really dig into what it was like to work on those productions, on-set tension and behind the scenes back-stabbing included. That's the level of insight I'd hope for from an Ultimate Edition.
If you can't access production staff for interviews, other options could include narrated biographies/filmographies of the crew. Another alternative I'd find interesting would be a featurette about the cyberpunk movement in general, charting its inception, influences, key works in different media and countries, and its lesser known examples.