Ramped channels are functionally the same as the non-ramped ones, they simply look different and allow moving through them.
Lollerskates. They're functionally the same, except that they behave differently!
I fully support a carve downward ramp designation. I used to think (3 days ago) that it was redundant and silly, but it clearly makes some things easier that were annoying some people and it is a reasonable adjustment for a specific use (despite that not being the intended purpose).*
I also support a revert to the previous channeling functionality that's nerfed to prevent impromptu defenses. I don't see why you'd need a double designation - just make it take 5 times as long to dig out the channel. The initial problem this was intended to solve was apparently the speed with which such a defense could be
erected sub-rected un-rected sub-structed dug out, not the digging of channels from above.
Attacks by ninja trees would probably be handled well by a Cancel dig: tree-bearing floor tile announcement.
And hey, I'm totally behind channels that look like that picture you posted. Those don't appear to be easily accessable ramps. A channel doesn't need shear vertical sides to deter attackers - that thing (minus the road-ways) looks like it'd be a pretty effective defense against gobbos and essentially useless as an access ramp. Any dwarf told to cross that channel to go fishing is gonna go Attend Party. The game is an abstraction, the actual area of a tile is indeterminate, the actual shape of the landscape is indeterminate. A channel is only a square-walled hole in your mind, it needn't be viewed as such for it's function to remain a valid supposition. Once this stuff:
* Ability to get to upper level without having to construct permanent building (ramp or stairs). Ladder that worker can pull up when he is done or just ability to grab edges and pull himself up.
* Ability to remotely breach wall (rig wall to collapse, link lever and pull it.)
makes it into the game, by all means, remove channeling completely (I also eagerly await smarter enemies and seige towers, that's gonna be awesome). I don't mind a bit of extra work to get what I want done done. But until then leave appeals to realism out of it. In order for them to be valid you have to ignore all the other reasonable abstractions the game already makes. Doors for instance. You don't need mechanisms (hinges) to hang doors. And for good reason - it'd be a huge pita. It's far simpler (and much more fun) to assume that dwarves got crazy 'stone-fu'.
*I will say that part of what I love about this game is figuring out
how to do things like strip-mine safely. I guess a lot of those sorts of things are bugs or technical issues that are yet to be resolved, but I always enjoyed figuring out the work-around even if it meant mining the wiki.