Couple of things I think would work in a jacket:
Integral fleece that is zipped into place and can be unzipped if it gets too warm. I have a Schott jacket with this feature, the fleece unzips and can be worn as an item of clothing normally (can supply photos if needed).
Think about the whole area around the cuff/glove interface. This area has most of the movement when actually riding (twisting the throttle, wiping your visor, hand signals etc, etc). How often have you got all your gear on and spent time getting the sleeves and gloves set up 'just so' for it all to let water or cold air in within 20 miles?
I have an Enduro jacket from a French company, Shift, that has a thumb loop built into the sleeve, this keeps the sleeve inside your glove all the time. The design needs some adaptation so that the thumb loop is inside your glove but your outer sleeve is over your glove (hope this makes sense). Again I can supply photos.
The whole area around the neck needs a lot of thought, you need to be able to have it open in warm weather, closed close to the neck in colder weather and maybe unrolled right up under the chin in very cold or wet conditions.
Make all the zip pulls BIG and very strong, even the Aerostitch ones can be too small and fiddly in very cold weather with winter gloves etc, also put a secondary closure system (press stud or something ) at all points where a zip starts. Zips have a way of working loose if the start is under tension.
Maybe look at a pocket inside the back of the jacket that can allow you to fit a back protector in whilst still being able to use the protectors belt and braces.
Velcro tabs or some such on the front to hold comms cables and hydration pack lines to stop them flapping about at speed.
Innner pockets that allow the user the choice of using closed cell armour or not (elbows, shoulders etc)
Then you just need some matching pants!!!