Don't hate the ribbon people. The ribbon is your friend. Embrace the ribbon ... or just hide it. Maybe a full-out good old-fashioned menu for all the people who don't like the ribbon. They would duplicate each others functionality and you could choose to display either one or both.
The abillity to create iso games easily.
I'm surprised more people haven't asked for full 3D support. Developing a 3D game is far too much work for me, but maybe someone else wants it.
AI behaviour? - This can be a distant consideration, but maybe creating an AI behaviour that performs simple tasks as chase down a character or try to avoid a character once it's approaching? Probably won't work since it's an abstract concept but it can be at least considered.
I really like the idea of more built-in AI support. I think this can be one of the toughest aspects of game development.
zooming out of event sheets
Maybe something like MS Paint does it. Ctl + Pg Dn would zoom you out two or three wheel clicks and Ctl + Pg Up could move you back in to 100% zoom. I'd like to see something like that for zooming in/out of layouts too.
* A new and powerful bone editor.
* Collision groups (an object could be in more than one group, to collide, two objects would need to be in the same group)
* Groups of layers (in order to allow us to apply effects on more than one layer)
I think the bone behavior is brilliant and unique. It's a great part of Construct. But maybe there could be a few built-in movements like walk, run and jump for a "standard humaniod." (i.e. shoulders, elbows, hips and knees) These could be edited for custom movements (maybe adding a tail or wrists and ankles) or could be used as is.
Also, I really like your two grouping ideas ShadF.