therefore, the old 9/10 is the new 11/12 ~ 13/14
No that's the point, you can't compare the new lvl 6 and 7 with anything in the old system, since it just wasn't there. The new lvl 6 and 7 are just the new top of the bill staff members.
If you had a lvl 10 in the old system, you can be satisfied with the lvl 5 now, there won't be a change in training speed or whatsoever.
I agree with KingJames, this sure is a great improvement to the staff system, nice job!