This seems like progress and a clear method to outer indexing will help many users. As for names, I prefer .ox and .vx for shorthand of .oindex and .vindex. I don’t like the .ox_ or .o_ syntax. Before any deprecation warnings or any other warnings are added it would be helpful to have some way to set a flag on Python to show some sort of HiddenDeprecationWarning (or OnlyShowIfFlagPassesDeprecationWarning) that would automatically be filtered by default but could be shown if someone was interested. This will allow library writers to see problems before any start showing up for users. These could then be promoted to Visible or Future later.