The Dangler, much like the Shrugger, is supposed to give you a window of opportunity to assign a follow-up skill. In a game without rewinding features, such as Lemmings 2, this is pretty vital.
In NeoLemmix, you can assign a Shimmier to a lemming a couple of frames in advance, and it will still be applied once the lemming reaches the appropriate spot. Still, that window of opportunity is pretty small, compared to having a dedicated Dangler state.
The Dangler should also affect Climbers and Rock Climbers in Lemmings 2, if I remember correctly. Importantly, while I always thought a lemming had to be a Rock Climber in order to transition from shimmying back to climbing, that is not actually the case: Even regular Climbers turn the upward corner, transitioning back from Shimmier to Climber.
The main weakness of the L2 Shimmier, compared to the NeoLemmix / SuperLemmix Shimmier, is that he can't shimmy up inverted 45° slopes (1:1 length-height ratio), but only flatter ones (2:1 ratio). For the 1:1-ratio slopes, you need the Rock Climber in L2 - which obviously has the side effect of the lemming looking in the other direction, compared to shimmying up a sloped ceiling.
I haven't tried what happens in Lemmings 2 when a Shimmier who is also a Rock Climber reaches an inverted 45° slope. Will he transition back into a Rock Climber, just like he would do if reaching a 90° corner? Or will he fall down?
EDIT: I've tried it out now. Indeed, a Shimmier who is also a Rock Climber will transition to a Rock Climber when reaching an inverted 45° slope. This isn't necessary in NeoLemmix / SuperLemmix, because Shimmiers can already handle such slopes on their own. It would however be required for 90° turns.This would mean that only slopes steeper than 90° (those with a 1:2 length-height ratio) could still stop Shimmiers, because regular Climbers can't overcome those (and we don't have Rock Climbers in NeoLemmix or SuperLemmix). The only way a Climber could overcome such an obstacle, though, would be by always transitioning into a Shimmier for one horizontal pixel, after which he would automatically transition back to a Climber for the two pixels in height gain. Meaning, this would require the player to keep spamming Shimmiers on a regular Climber.
The thing about this new behaviour is: If Shimmiers can turn upward corners, how can you still stop a Shimmier? Gaps in the ceiling no longer work as easily. Unless of course you create a height of two pixels per 1 in length (1:2 ratio) - which right now makes the Shimmier stop, and would make him climb with the new behaviour - followed by another horizontal piece of ceiling.
This would require another Shimmier assignment if the lemming is supposed to continue. If no such assignment occurs, the only minor difference would be that, rather than falling down immediately as soon as the Shimmier reaches the 2-pixel-high terrain, he would climb up those two pixels, then dangle from the ceiling above them, and then fall down (for lack of another Shimmier assignment).
In short:
One of the potential obstacles Turrican could add to his levels, in order to continue to enforce the Shimmier-Freezer-Cloner-Jumper combo, would be short sloped overhangs with a 1:2 ratio. This can be done either by extending the vertical overhang into a slope, or by cutting such a steep slope into it (=by erasing terrain).
Either way: Just make sure not to provide so many Shimmiers on such a level that the player could overcome this obstacle by Shimmier-spamming, as explained above, instead of using the much more elegent four-skills combo.