u/JulyAt5am

There are tons of threads for 404mk2 where users speculate about some missed opportunities (and it still receives new firmwares, after all these years). So, I decided to add my two cents taking into account that it has a VST form (read: not abandoned) that somewhat doubles the chances. Anyways, it won't hurt, and sharing ideas publicly is the only way for Roland (the email support is restricted for such "wishes" due to some legal problems).

• the first thing that comes to mind is that it could be significantly more flexible if a player could assign its pitch and amp modulation only for one oscillator with shift button. I don't suggest filter, because, obviously it can be only global, but the basic two could be applied to an oscillator easily. In a patch menu player could specify which one is controlled with shift for each knob (1, 2, 3, 1+3, 2+3).
• "color" LFO modulation could benefit from the polarity setting, also accessible with shift. The idea is that two oscillators could be bound to the same LFO, but move in different directions with a definable starting points.
• the 2nd LFO variation where one LFO modulates another one: it could also benefit heavily from secondary controls. While holding shift the rate knob could control its speed and the waveform could allow choosing different basic waveforms.
• when you record automations with the sequencer it doesn't record sequencer settings. for example, automated "gate" could be pretty cool. and you know the solution I will suggest – shift button. when the realtime record is on holding shift could force these settings to be recorded.
• shift + delay time for fast access to its feedback (and motion-recording it), shift + level to access to DlyDirLev buried in menu (you can kill dry this way)
• alternative panning for the performance mode (like in JD-990 for example) to make each patch sound in different channels each keypress. One layer can be centered, the other is panned – or both.
• shift + tempo sync for tap tempo
• sequencer: it doesn't show recorded knobs and their values when you select a step with them (empty 4 slots) – would be nice for editing. also, in step recording when you edit a value by moving some knob it would be great using arrows to select a specific value (knobs can be too sensitive)
• sequencer: some parameters interpolation between steps would be great when it's used as a motion recorder, because even at 300bpm you can hear a steppy nature of values' changes.
• sequencer: the way to rollback all the values changes made with a sequencer when you stop it
• just a thought for a theoretical mk2: as long as we treat the sequencer as a global modulator it would be great to have a knob to adjust how far the modulation goes (maxed knob would mean values you've set/recorded; minimizing this knob's value would scale down linearly all the values within a sequence). Sure, it could be made with some shift + something, even in this mk1 form, but one can wish.
• another one for some possible future successor as long as we're here: amplification bias per oscillator (like in JDs; similar to filter's "key +/-"). For example, to lower sub oscillator's volume in higher register.

These are pretty basic ones that don't seem to mess heavily with the UI or its architecture, but could significantly deepen sound design capabilities for the already (almost) perfect tool. Edit: there were only basic ones, but I edited the post a couple of times, so.. yeah.

Feel free to add yours too or share your thoughts about the synth. The photo isn't mine btw.