As a SC user, i very much disagree with this opinion. SC's copy skills are not designed to be used in this way for my perspective.
An example situation for the first job copy skill (Plagiarism): You can't just get the skill from an enemy on the fly during a fight then use it. It will be like Get hit by a first job skill -> Preserve (skill) -> Alt+S -> Misc -> Put the skill in a hotkey or left click + Alt+S -> Click it on an enemy.
This time frame of doing that just to be able to use the skill you got on the fly is very risky while being vulnerable during the time you do this, or its also possible for the skill to be changed already before it gets used if preserve didn't get/yet used.
For the third job copy skill (Reproduce), it will be like Reproduce -> Get hit by a 3rd job skill -> Recast Reproduce -> Alt+S -> Misc -> Put the skill in a hotkey or left click + Alt+S -> Click it on enemy.
You can already imagine how messy that will be for both copy skills. Indeed it's possible to be done that way, but it's a very risky and a very unlikely thing to be done in RO if you know how the game's fights works, you can be killed very quick in that moment.
To me, the essence of SC's copy skills is for players to be innovative on combinations they can come up with, to utilize their comprehension and knowledge of the game and use them effectively to win fights. SC embraces the effort of thinking rather than spamming one skill to win. Planned ahead of time, and backed with the element of surprise.
I neither upvote or downvote the suggestion, i just disagree with this opinion.