Five points might be too much, but if it was made dependant of the level of research it might work out better... Like +/- 1 at level one, 2 at level 2 and so on...
Hmm.
Maybe it would be better choosing the adjustments with 3d6, and every scale of magic/drain adjusts this by one.
If you got under 3, you get adjustment of -2, any of the numbers 3-5 gets you a -1, over 16-18 gets you +1 and 20/21 gets you +2. In the land of magic+3, you would have(3d6+3), so no minuses! And the reverse, no plusses in the land of drain (3d3-3). Oops. Except for Ulmish smiths. How do the themes affect them? Oh, the open-endedness IW is fond of! Well, there we have a problem...
Damn.
This is getting complicated. No wonder they are not adding our every idea to the game! Although it might also be because our ideas are not good...
