BTW: I absolutely love the cross-signing move and riot/matrix in general! :) Thanks for your great work on this!
It's possible we'll reintroduce this once cross-signing has been fully adopted though; it's tricky because we need to distinguish between encrypted rooms where you simply don't care if random users have unverified slides... versus ones where it's a disaster if an unverified session slides in. Finding the right UX for that is tough, but we think the current balance is an improvement.
That is really a tough UX problem... Maybe a room could have a "sensitive content" flag that is enabled by default for one-on-one chats and can be manually enabled for group chats.