When our group's vizier (second in command) gave this student permission to attempt to convince the group, it was clear that he was not entirely ready to do so. However, while I prefer the way later editions refined the combat system (which is still too cumbersome), I do have a soft spot for THAC0 as it was part of how I originally played the game. Thus, I helped explain the cumbersome calculations required to understand THAC0 and the concepts of negative Armor Classes being preferred.
Now, I know that even this brief bit of jargon has already lost many people, so I just want to say that during my explanation, I was overcome with a strange nostalgia to play in that antiquated system again (much as the student who presented the idea probably hoped). A convoluted as those rules were when compared to more recent editions of D&D, it appears that I still have a vague fondness for them in my mind. The students seemed to enjoy the retrospective that I provided, but without my nostalgia, they had no desire to switch to that older system.