It's implemented that way to handle negative values. So 2(L would be [1,0,-1,-2] for example. I don't recall having needed that functionality though. Ÿ is probably better suiting for handling negatives since L can only ever start at 1.
All very good ideas. I can't say I've ever needed P/O to work on mixed lists, but I can't see a drawback to them having this function. The suggestion for à/ß might need some consideration as they could no longer be used to pop the largest digit in a number. Doing Ws\ over ß is a bit clunky. Haven't personally used ß a lot though, but I've seen it used by others more.
@KevinCruijssen I had these as alternatives. Where the last one was the most interesting imo printing backwards, but unfortunately finding out the direction to start with got quite expensive
@KevinCruijssen I assume it's due to vectorization. It might be logical to have a special case for the empty list, but maybe that is not what you'd expect in some cases. Unsure of what the best behavior for that would be.