How to improve the start screen for legacy apps
Problems with its current state
The new startscreen has been the subject of much criticism since i was revealed that it would replace the start menu. Microsoft has made some good arguments why this approach is better than the previous versions of windows such as the amount of content displayed, spatial recognition and the size of the click targets when using a mouse.
However, and this is from my own experience, the support for legacy applications is not as good as it could be. For instance when you install software made for earlier versions of windows it usually dumps a whole lot of useless shortcuts in your startscreen and you have to manually remove any unwanted shortcuts.
Your startscreen will be clustered with shortcuts like this
Microsoft has talked about how it uses it telemetry data in designing some of the new features (such as ribbon for windows explorer) and it is this data that could be used to cleanup the startscreen. The user have the ability to organize the startscreen however he see fit but my idea would be to use this data to help the user in this regard.
The intelligent startscreen
First off, you could use the data to see which shortcuts are actually being used from a program. Older software especially used to dump uninstall links and links to homepages in the startmenu. These are hopefully not going to show up a lot in the statistics (and if they do it's probably not the best piece of software). It would be fairly simple to discard these and recommend only placing the actual program on the startscreen. But what about programs that comes with utilitize such as the Adobe Creative Suite or Microsoft Office? My idea would be that you simple made a new expandable tile that said "Microsoft Office tools" or "Adobe Creative Suite tools" and added all of these here.
Another concerns entirely is the concern over why you would want to giant icons of your programs take up all of your screen. This argument has been many times and i think it's a fair point. The answer to this question is live tiles and collaboration. Let me explain:
The future holds an ever greater need for collaborating on projects, everything is converting on a point where multiple users can co-create content at the same time. Microsoft has implemented this feature in Office and lots of projects (http://sunglass.io/#democanvas + http://layervault.com/) especially on the web has this as its focus.
Metro could be the hub that keeps track of all this. Open the startmenu and notice that your photoshop tile has a new message that a person from your team has reviewed your image. You could even have a project tile that keeps track of all that goes on in a project such as word docs, calendar and meetings, notes or presentations.
This would of course depend largely on Microsoft improving skydrive integration a lot or 3. party developers embracing live tiles.
Other than what i just discussed i would probably make it so that when you search you get all the results but separated instead of having to change the filter.