BIP69 is a pretty under appreciated bip that defines a standard ordering for transactions inputs / outputs.

There's quite a few obvious advantages to the approach, like making it easy to verify correctness, or making it easier to write unit tests. But I think the most important aspect is it helps users verify their wallet isn't maliciously leaking information. Granted a malicious wallet could try leak information via the nonces, deterministic signing helps make that detectible with access to the private keys.

As some wallets have already moved to bip69 (and unlikely to consider moving back) it would be very beneficial if core moves in the same direction resulting in better transaction uniformity for everyone.

(And a bounty for fun: if this is merged in the next 3 months I'll offer 0.03 BTC to the author :D)