Now that we have events to text, and we know the Scirra team have expressed interest in trying a text to events parser, I pray that we're one step closer to a text editor based version of the event sheet.
Being able to type an event sheet, I'd buy C3 for that alone. Add some decent code hinting and I'm a customer for life.
I was surprised with how much I enjoyed being able to dock windows literally anywhere, and split existing views (want two side panels to act as event sheets, you can!); off the back of this, I'd love the following:
1) Save custom layouts to use from the settings menu.
2) Being able to dock the preview window.
C3 also has an odd and slightly annoying habit of launching the preview window in the bottom right hand corner of my screen; but this is on a second monitor for a Surface Pro 4, which are absolute bastards when it comes to dual monitors...