Now that I've taken the plunge into Vegas 15 I feel emboldened to make new feature requests :).
Three things I'd love to see are:
1. Multiple tabbed timelines like in Premiere. This is a really efficient way to work with certain types of projects.
2. GPU acceleration for editing. I'm currently using the Proxy workflow but other programs like Edius and Premiere can play back native 4k footage more efficiently so I know it can be done. Nothing like a slow preview experience to hamper creativity.
3. Better color correction tools with power windows. Premiere has really upped their game in this area and Resolve well... enough said.
So what features are on the top of your list?