Link Skill System

How is that OP? It's just convenient.
There's a 1 time per day limit when assuming link skills, but other than that, you can give it to any char.

That was his point, the usual reaction to someone saying "It should affect the whole account" is "It's OP!"

Which of course it isn't, for the reasons you just said. The daily limit is actually fairly stupid and doesn't affect balance at all, it just makes it inconvenient.