As with BG2, BG1's SPELL.ids reveals what the missing spells were intended to be:
SPPR215 - Resist Cold (1)
SPPR505 - True Seeing (2)
SPPR506 - Wall of Fire (3)
SPWI109 - Hold Portal
SPWI204 - Fog Cloud
SPWI216 - Wizard Lock
SPWI315 - Waithform (4)
SPWI307 - Invisibility, 10' radius (2)
SPWI403 - Fire Shield (5)
SPWI408 - Stoneskin (2)
SPWI409 - Wall of Fire (6)
(1) it seems Resist Fire and Resist Cold were originally going to be seperate spells, but were later combined.
(2) present in BG2.
(3) SPPR506 is Iron Skins in BG2.
(4) already in BG2 UB, of course.
(5) present in BG2, though seperated into Fire Shield (Blue) and Fireshield (Red).
(6) SPWI409 is Contagion in BG2.