A more interesting idea for Echo's Ult could involve her copying the last enemy ult used.

I think this would be far more balanced and interesting then the current version. Instead of the possibility for multiple ultimates for the value of one, which is ridiculous honestly, she would have a one-time use of the last enemy ult used. I think this would be more engaging and interesting then the current design and lead to actual planning.

From the perspective of the Echo they can keep their ult charged at 100% and the icon will switch to show them the last ultimate the enemy used, and they need to decide while their ultimate is ready exactly when they're going to pull it out. The enemy team has to remember what the last ult they pulled off was, and maybe organise their ults to be popped off in an order that least benefits Echo.

If multiple Ultimates are popping off simulatenously, Echo can try to throw her ultimate out at just the right instance to get the ult she wants and in all the havoc the enemy may also not know what to expect.

Plus it fits her name really well.