Well making a complete and comprehensive list of all features would actually be a hell of a lot of work. I've written the equivelent of an architect's specification for software products. Trust me, it takes a lot of time to do it right.
So I will just give a few main points, assuming anything these days will have the basics like 4 bands or more of EQ and Dynamics on every input and output, etc...
1. Scene Control - that can work like a cue sheet, allows multiple scenes with fade times to run simultaneously, and the scenes can easilly be controlled by some sort of simple trasnport on the console, plus accept both standard Musical MIDI commands (i.e. program change, MIID notes, etc..) MIDI Show Control and MIDI Timecode inputs for the triggering of scenes without the need for some intermediary software or hardware to handle the show control aspects.
2. Full Client Server connections between the UI and the Audio Engine. So that multiple users can all log in and completely customize their UI for what their job requies. This would include software remotes that run on both Mac and Windows and full crossplatform support for tablet remotes as well. From as much as I've seen the only ones that get this right in my book is Allen and Heath and Meyer's Dmitiri (but that's such an expensive beast that it's hardly in the same leage as most digital console except for the most expensive Digico)
3. Full Matrix routing for all inputs to outputs with time allignment delays at every input, every output and every crosspoint in the matrix.
4. Typical DCA behavior as is implemented in most Yamahas and others that actually have DCAs, Any volume control point in the entire console should be able to be assigned, input faders, output faders, any sort of bus faders, even aux send faders from individual channel strips, etc.. They should be virtual and unlimited so you never run out of DCAs and easilly resassign using Scenes. If there must be a limit on their number it should be something ridiculously high like 128 or 256 or something like that.
5. Control surfaces should be modular and come in all shapes and sizes and attache directly to the computer network so they act just like another client that logs into the server.
6. I/O modules should be completely modular and sit on a simple computer network, with Dante being the most likely candidate for data transmission to and from each node. Preamp input gains should be able to be recalled via Scenes and have a control built right into the UI of the console.
Oh and I want all this to cost no more than a Yamaha LS9-16 or maybe a Behringer.