Wall- and ceiling-running would not only look incredibly silly without a full set of running sprites for each angle (and don't say "just use spinning sprites", because that's a visibly ugly hack that goes against what anyone playing the game would expect to happen), but would also be a nightmare to get the camera to work well for. Perspective in software mode is pretty much garbage, so tilting the camera up to follow the player wouldn't work (and doing that even in OGL, with proper perspective, would just cause nausea), but just leaving the camera straight would make it impossible for the player to see where they're going once any vertical momentum is involved. This leaves cut-away views, which would then disconnect "move forward" and "move away from the camera" in non-analog mode. If you're proposing to automate the process of running through a loop to avoid that, then you might as well just fake it with a zoom tube.