As an innovating sort, the idea intrigues me, but
since most people are used to dealing with 5's and 0's,
this might be somewhat impractical. Some of us can't
handle being able to add tens and twenties unless it's
currency.
If I understand this correctly, the other problem is
the assignment of 1 point to a "very difficult"
question. While its impact to matches may be minimal, the
fact is that you are also punishing the rare
individual who may actually know the answer by making it
worth only one point. I would ask why not make it worth
15 points to reward more
knowledge-in-depth.
When you go about writing/editing your questions,
obviously have a goal for bonus scoring (as Anthony pointed
out), and make sure that your expectations of the
difficulty level of the packets are reflected in the scoring
efficiency.
On the other hand, I also remind you, you need not
have to have two- to three-part bonuses. You can elect
to have just a one-part followup/bonus kinda like on
Ben Stein (or Kentucky's HS comp).