As said, I will split up my main feature requests into several.
At the moment there is no way to properly connect Notion to Studio One realtime, as ReWire doesn't work well (no tempo changes in Notion, no repeats). To connect the 2 in realtime, I use a 3rd party tool LoopMIDI, basically a software based internal MIDI cable.
Works, but it's a 3rd party tool and I'd love to have something that is officially supported and does not have the downsides this solution has. :)
I realize I forgot something:
The lack of synchronized start/stop, record, transport, etc.
I use a Faderport 8 with S1. For writing, it is fairly annoying that transport doesn't work, basically rendering part of the FP8 useless.
But when a song is in it's final stage and I want to actually record it, there is no way to sync start/stop/rec with S1. The only way to record, is pushing "record" on S1 and then "play" on Notion. (Or pushing the Notion notes into S1, losing all custom rules along the way.)
So the realtime integration is really a bit more than just realtime sending note data to S1, it's about transport as well. A bit like ReWire does. (But as S1 *has* to be ReWire master and Notion can't make proper use of a device like the FaderPort, simply making Notion ReWire master is not an option at all.)