Besides being a hard fork, there are some undesired effects.
- similar to malleability it changes the transaction ids of your valid inputs
- it may invalidate your partially signed transaction that you got from a third party on a common multisig address
- it may make your bitcoins lower priority, since their age is diminished
How could the first point be practically exploited? I'm failing to see any issue with inputs being changed. If you're expecting a payment with a certain txid, that txid will still exist even if it is later combined with other utxos right?
I'm not familiar enough with how the second point might pose an issue, do you have an example?
For the third point, this is a valid concern and maybe the priority/age formula would have to be modified not to penalize consolidating utxo's.