I'm very surprised to hear this; I wouldn't expect as much problems with the ceiling as with the sides.
When you reference holding pits which are restricted through the ceiling; do you mean a pit that reaches the ceiling and the ceiling stops the climbers? I think of maybe one PimoLems level like this... When referring to lemmings walking near the ceiling, so that most of their body is not visible, I would agree that I think whether solid or not, this should be allowed, but I say I personally don't like a level mandating this kind of thing in the first place [might I reference a certain level called Technoir...]
I would vote for letting all this be on option, simply for the benefit of existing levels.
Mostly it are climber walls, but
a lot of them and I mean even the walls which are not needed, but could cause the player trouble, because I don't want to punish the player for using a climber ever so slightly different especially in the early ranks.
Obviously
I vote for deadly, as it prevents backroutes from happening + doesn't make it nessesary to stratch out a level as much to keep the player from abusing the walls + using the sides actively in a intended solution is kinda dirty.
But here I have to say even with
deadly walls they
should not actively be used as a "deadly wall" as I mentioned in another thread.
They should interfere as little as possible in a level. If the player tries to build a bridge out of the main area they should still punish him, but using them to compress the level size to a minimum is not the correct way here I think.
Also making your levels independent from the solid sides isn't much work I can assure you, möbius
Example from "Return of the tribes" currently the sides are solid, but as I know Nepster this will change:
Here sth like a little water pit left and right would indicate directly that the climber cannot go to the sides, instead of relying on the deadly sides. This would make the level slightly bigger, but I think it is worth it.
And now an example from my single levels to show the opposite case:
Here I originally planned to use the solid side, but Simon convinced me that a steel wall is much more honest.
This is still one of the most inconsistant behaviors across all Lemnming games and as a designer you should not rely on them regulary as part of the solution.
I originally wanted to make a "level design" topic about the not using the sides stuff and I still may do so, but for now this should work