* Malleability could be fixed by just skipping the signatures (the same data that SegWit would segregate) when computing the txid.
That _is_ segregation of the signatures up to completely non-normative ordering of data transferred. Segwit could just as well order the data into the same place in the serialized transactions when sending them, but its cleaner to not do so.
* GREATER bandwidth savings could be obtained by providing API/RPC calls that simple clients can use to fetch the data that they need from full nodes, sans the signatures etc. This enhancement would not even be a soft fork, and would let simple clients save bandwidth even when fetching legacy (non-SegWit) blocks and transactions.
This would be no greater and it would have _no_ security at all. The clients would be _utterly_ beholden to the third party randomly selected servers to tell them correct information and they would have no way to verify it.
I normally don't expect people advocating Bitcoin Classic to put security first, but completely tossing it out is a new turn. I guess it's consistent with the latest validation removal changes in classic.
* Pruning signature data from old transactions can be done the same way.
Has been for years.