As you noted, when Ableton records multiple channels to a single track (when you select "omni" as the input channel) it sums all of that data to a single channel, which means that the dimensions of touch will no longer be polyphonic –modulations would be heard equally on all notes.
However, there are workarounds for this that will not require you to give up on MIDI recording. To fully unlock MPE expressivity in Ableton, you will need multiple MIDI tracks and one host voice track in your Ableton project.
One host track – this track will have no MIDI input selected, and will host a multi-timbral plugin like Equator.
Several voice tracks – these tracks will not host a plugin, but will receive the global and note channels from the Seaboard, then send them to the host track. You will create several voice tracks according to the channel range you select in ROLI Dashboard.
This guide mentions the RISE or GRAND specifically, but the process will be very similar when using BLOCKS and ROLI Studio - https://support.roli.com/a/solutions/articles/36000019096
Hope that helps,
Depending on what audio interface you are using, you may be able to open your Roli Studio Player outside of Ableton and record it from its standalone instance into an audio track inside Ableton using the same method as me.
I have an Universal Audio Apollo audio interface and I have it setup with virtual audio tracks. I set my output in the Roli Studio Player audio/midi settings to send to the virtual audio tracks and then they show up in live as audio inputs 5 and 6. I can't remember exactly what the setup process was to get to this point (you will need to toy with your audio input preferences in Ableton), but it's definitely possible to do this audio routing if you have the right interface. It's not an ideal solution and I would love MPE support from ableton, but its better than nothing.
I'm using Ableton's Live as a DAW and trying to find a way to have MPE, which is not supported by Live. I invested quite a bit of time and money in Live so would prefer not to switch DAW if possible.
If I give up on recording the MIDI and just record the audio out of the synths, it would make sene that Studio Player accepts the MIDI from the ROLI hardware directly (thus with MPE) while sending audio to Live. But when Studio Player is integrated into the DAW as a VST, it can only accept MIDI from the DAW, thus no MPE. One possible solution would be to have Studio Player as a ReWire Device so it would send audio to Live through ReWire. Is it something possible and planned?
Even when using the Studio Player+Seabord just for jamming without recording, as soon as I want a second track, e.g., a drum beat, then the DAW is needed, and with ASIO, having two applications playing sounds together doesn't work well, unless maybe there are multiple audio interfaces hooked to the computer. Again, having Studio Player standalone, receiving MPE by itself and sending its audio to Live somehow, would solve that issue.
An alternative to ReWire could be to allow Studio Player to accept MIDI from an external source even when running as a VST. Not sure it is possible though, as this might conflict with the DAW. Maybe in the end there is no better solution than giving up on MPE or switching DAW, but just exploring.