An editor would be key. Elektron not assisting with Rusty's editor is a real fail, but not creating their own editor is a double fail. I'm willing to be somewhat forgiving as I know they've been utilizing a lot of software development resources with Overbridge, but unless they are building a new Octatrack (and even then), there is no reason they couldn't throw some man hours into an Octatrack editor. At the very least it would help to increase sales for those on the fence who Google the Octatrack and find pages of complaints. Personally, I find I can make due with things as they are, but I'd really welcome some better methods of organization.
I don't see more static/flex machine slots as likely due to mathematical limitations. No worries, there are workarounds like chains. But Parts...give me twice as many Parts or more. 4 Parts per bank means I have to really limit what I can do with Patterns to get dynamic elements in songs. The more I grok them, the more I find them a problem. I'd change Parts every two Patterns if it was possible, but as it stands doing so means changing Banks just to access more Parts. Give me a new Part/Kit per pattern (like the MD/MNM) and I'll be infinitely happier.
Finally...midi scenes. I can understand the clusterfuck of sending multiple CCs for 8 midi outputs, but I'd be content with just using the 4 CCs on page 1 so I could control an external filter with scenes. Leave Page 2 to only be controlled with P-Locks and LFO, but damn girl, give me a little room to do my thing.
All minor gripes, but I think they are reasonable and addressable for a machine in 2015, especially when you consider that something like the Machinedrum had many of these things covered a decade prior or more.