Mimic to elite
Funnily enough GW1 has a similar elite skill to what you suggest called Echo lol. You would be able to copy one of your skills for a set period of time including its cd so it could be used multiple times as a copy of that skill.
I’d prefer a return to skills like arcane mimicry/thievery from GW1 which copied an enemy’s skill especially in pvp situations. It could lead to some really interesting fights and builds.