AHI support, for true 16-bit multi-voice sound support inside WinUAE. Basically, whatever capabilities your Windows sound-card has would become available for AHI-compatible Amiga software within WinUAE.
Better AGA support, since the current implementation is a little bit slow, and somewhat limited.
The ability to save and load the complete state of the emulator, so that if the game-saving doesn't work (due to floppy-disk emulation problems), you will be able to just save a snapshot of the entire "Amiga" and resume your game at any time.
Asynchronous Picasso96 RTG support. Right now, when the "Amiga" calls a P96 routine to blit a rectangle, the ENTIRE emulation is stalled until the blit has been completed by DirectDraw. I want to fix this.
Improved serial-support through a uaeser.device implementation.
Improved printer-support through a printer-driver on the "Amiga" which formats all printing as graphics and hands them across to the Windows printer-driver.
The ability to read/write Amiga SCSI or IDE hard-drives when connected to your PC. This would allow you to simply connect your Amiga's hard-drive to your PC and transfer across the contents.
Faster 680x0 emulation.
WarpOS API compatibility, so that an Amiga program with WarpOS (PowerPC) extensions could do a recompile for x86 and still use that extensibility.