Add the ability to run and/or fly
Avatar skin texture improvements
The ability to work with objects with scripts while in layout. Having to publish all the time to test things seems unproductive.
The ability to make experiences privately published while retaining the thumbnail. A use cases would be if you wanted to ensure you published version is behaving correctly. I realize that you could remove the thumbnail to not be listed, but if it's a temporary situation for testing (and often) purposes, it's easier if you don't have to hassle with removing and adding the thumbnail every time.
Some way for non-HMD users to pickup objects in a published experience in order to complete quests if there were a situation.