Seems fine, although the DTT change could still make cheating beneficial, because your opponent doesn't know what it in your hand. I mean, all of these changes give your opponents more opportunities to misplay, but DTT feels particularly tricky. Still, it seems like a good step.
It does give your opponent an opportunity to misplay, but I'd say the likelihood is ridiculously low--you'd have to be in a situation where you need something specific and your opponent doesn't know what that thing is, you'd have to find what you need as the 8th card,
and you'd have to have found something else in the first seven your opponent is likely to guess is what you need. In any other situation, the fix would always provide negative value over just playing things straight.
The success of an opportunistic cheat depends on making and acting on decisions at lightning speed. The more information a player has to process in order to determine if cheating could be beneficial, the less likely a cheat is to happen at all, because by the time the player finishes thinking, their window's already gone.
The scry rule reminds me a judge call that happened near me once. A guy targeted a Battlewise Hoplite with two Defiant Strikes, and he drew the cards before he had placed the counters on the Hoplite, which his opponent called a judge over. However, the guy had scryed before he drew, so they couldn't just call a missed trigger, they eventually rewound. This judge call was notable to me because it took a long time for the fact that he had scryed to be brought up, and it was very distracting for me as I tried to play my own match, which was actually getting to a very complicated line of play, but I find judge calls irresistibly interesting.
Not sure why they couldn't just call it a missed trigger--the opponent would get to decide whether or not the ability goes onto the stack. Or maybe this was under an earlier, less-good trigger policy.
Right but what if the card you "forget" to reveal isn't a creature. Your scenario allows me to keep a noncreature I drew with Domri.
I'm fairly sure Jman means a situation where his entire hand consists of nothing but creatures--in such a situation, it's not possible for the card to have been a noncreature, because there are no noncreatures in his hand.
The they'd-all-be-legal situation is raised fairly frequently whenever policy for these kinds of infractions comes up, but any judge at a Competitive-level event who ruled that you could just reveal everything would be deviating from policy; it's explicitly not a supported fix, so in most cases you'd actually be less likely to get that fix if you appeal to the (presumably more-experienced) Head Judge.