The reason I thought 2 AP would be a good number is because of what I expect will happen later in the game. In all my playthroughs, I have easily attained 14+ AP per turn on each of my characters. A +4 AP penalty would not have been very significant.
How did you do that? Not just with +Speed, I'm sure. Are you talking about Raistlin (and with Lone Wolf as well)?
If that's the case, not everyone will want to take Raistlin + Lone Wolf.