2 -- initial (unlisted)
3 -- Base (Possibly stubble)
4 -- Age
5 -- Age (2??)
6 -- Evil
7 -- Good
8 -- Skill
9 -- Skill (2??)
10 -- Will
11 -- Strength (Overridden By Skill)
12 -- Strength (2?? used in skeleton morph)
13 -- Weak (used in skeleton morph)
14 -- Fat (used in skeleton morph, also had some other flags set)
16 -- Evil (2?? used with hair morph)
17 -- Berserk (used in skeleton morph, also had some other flags set)
18 -- Teen (used in skeleton morph, also had some other flags set)
In the Hero Morph, each texture set (and skeleton/effects) is assigned an attribute.
Take the old age textures and change their stat to will. Both the Old age and the will tats will now appear with the will stat.
If you talking about the actual spell usage causes aging. Then that won't be possible.