Could care less about the helmet. In the lore, it wasn't/isn't a big deal for Spartans to take off their lids.
My problems with the show however, are numerous.
- Halsey decided early on that not being honest with the Spartans was a terrible idea. So them being kidnapped child soldiers is not a secret amongst the corp. In-fact, most embrace the Spartan life.
- The covenant, specifically the Sanghelli, see humanity as bugs pissing on their church relics. Them accepting a human into their fold as some herald is a big no-no lore wise. Of course, the religious scorn the covenant have for humanity was built on a lie by Truth, Regret, and Mercy. They took many steps however, to ensure the secret would never get out. Because if it did, it would lead to a schism within the Covenant.
- LOL, countless humans (probably the majority) have the gene(s) to activate forerunner tech. John was never special.
- Why make a whole new team of never heard of before Spartans, when you have a library of loved characters from the lore to choose from (blue team).
- The Byzantine Politicking within the Covenant in the show is sorely missing. I think it, and many other aspects of the covenant, are being glossed over Becuase the show runners dont trust their creations (the covenant), that's why they introduced a human into their midst.