I actually think the thing they writers most likely to do, and indeed have, isn't to actually alter the Echo as it stands (largely because it's super vaguely defined as Mikko said), but rather to add in an element of unreliability to it. Like how the Exarch and Elidibus flashbacks in Shadowbringers were very obviously spotty and hiding information, or in the Endwalker patches, flashbacks so far-flung that they're providing nothing resembling useful info (some of which weren't really Echo flashbacks, but serve the same purpose). You can start seeing them alongside other abstract and artistic ways of depicting past events, too, like Emet's it-turns-out incomplete account of Amaurot, or the phase transitions in Tsukuyomi or Eden's Promise. So yeah, I think if we see curveballs thrown at us, it's more likely to be that the Echo vision we're being shown isn't the whole truth, or an actionable truth.

Now if you're talking about other people who have the Echo, all bets are off, because they've never been especially clear about what that means. The core writers never really push it that far--Krile's got a different sort of Echo vision to us, but rarely ever uses it. Matsuno liked using it for Mikoto and Misija, but that definitely seems like a 'him' thing. So not only is it hard to tell what they could do, it also doesn't seem likely that they'd do much of anything.