1. Give the sequencer the functionality of the old MPC system used on their old workstations and stand alone sequencers. Specifically, the ability to list the MIDI events in rows and alter them directly while scrolling through the list. I did a track on the old W-30 sampler workstation one time in which I played a lead - poorly, but I fixed it easily by entering the notes in step edit. Then, since the synth I was driving with that track responded to velocity, I opened up the Microscope Edit screen and located the cursor on MIDI velocity parameter. I scrolled down the track using the arrow keys and tapped a key on the keyboard to input velocity directly, and made a wonderful build of timber and volume in the track with ease. The parameter would update with the velocity value of the key as I struck it, only putting in the velocity and changing nothing else. KORG will allow this in their sequencer too, but it's dreadful because you have to hit the Enter key each time you want to do the same thing, making the process tedious.
2. Make a VA model of the System 700 Modular synth, for both the Fantom and Jupiter-X. Roland could release a programming app for iPad, Android, Windows and OSX as Nord did with their Nord Modular. The Fantom could be programmed directly using its marvelous Touch Screen and programming interface. Make it polyphonic as with the Nord Modular and Arturia Moog Modular V. In fact, how about a Moog Modular model while you're at it? I understand that polyphony would be reduced based on the complexity of the patch, but a modular patch wouldn't have to have a ton of polyphony. Just six or eight notes should be plenty, four would work.
3. Make a programmable/editable physical modeling synth as Yamaha did with the VL family. Polyphony wouldn't need to be very high. Make a USB breath controller to drive it, and which can be used with any synthesizer.