[Klutz]

Even better:

Faerie Mage (50 bonus points unassigned): 25 Str, 60 Int, 35 Pie, 30 Vit, 55 Dex, 60 Spd, 45 Sen

Assigning initial bonus points to get Int as high as possible and get as close as possible to Bishop min requirements, we can get:

Faerie Mage, Level 1: 25 Str, 77 Int (+17), 52 Pie (+17, 3 short of Bishop min), 30 Vit, 55 Dex (+0, already at Bishop min), 66 Spd (+6), 55 Sen (+10 to Bishop min)

Level 1: 77 Int, 66 Spd, 52 Pie
Level 2: +3 Int, +3 Pie: 80 Int, 66 Spd, 55 Pie (Switch to Bishop)
Level 3-6: +3 Int, +3 Pie: 92 Int, 66 Spd, 67 Pie
Level 7: +3 Int, +3 Spd: 95 Int, 69 Spd, 67 Pie (Int maxed at level 7!)
Level 8-17: +3 Spd, +3 Pie: 95 Int, 99 Spd, 97 Pie
Level 18: +1 Spd, +3 Pie, +2 other: 95 Int, 100 Spd, 100 Pie (Pie and Spd maxed at level 18)

7/18/18 is definitely better than 12/18/18, at the cost of spending one level as a Mage instead of a Bishop. Similarly, the Elf Bishop can go from 11/19/20 to 8/19/20 by spending one level as a Mage. Note that you can never do better than sticking to a single class the whole game for purposes of maxing all your attributes that you are interested in, because extra classes can only add requirements, never take them away. However, I think this is the best example of what you were looking for initially: using the freedom you get from a simpler base class to get a jump on your primary attributes.

The simple reason that the Priest, Alchemist, and Psionic are all suboptimal to start with (for an Int/Spd/Pie Faerie or Elf Bishop) is that every one forces points to be added to something other than Int, Pie, or Spd beyond what a Bishop normally requires. Priest forces Vit to 55, making it the most wasteful: 20 points "lost" for an Elf and 25 points "lost" for a Faerie. Alchemist forces an extra 5 points to be "lost" to Dex and Psionic forces an extra 5 points to be "lost" to Sen. Mage is the only caster class whose extra requirements over Bishop are strictly helpful for the Faerie or Elf: in this case, +5 to Int.