Existing behavior: There are certain spells that projected images/simulacra may cast but otherwise do nothing. Also, both projected images and simulacra are able to cast simulacrum (thereby creating a copy of a copy), which enables many different exploits.
Expected behavior: Certain spells should simply not be castable, preferrably not even selectable from projected images/simulacra.
How to reproduce this: have a spellcaster created by simulacrum cast project image. Or a caster created by project image/simulacrum cast simulacrum. They could also attempt any trigger/contingency spells except no spell icons will show up.
Suggested implementation: Remove a certain list of spells via instances of effects in PROJIMAG.spl and SIMULACR.spl. This will require instances of opcode 172 to remove the following spells:
SPWI420 (Minor Sequencer)
SPWI703 (Project Image)
SPWI710 (Spell Sequencer)
SPWI809 (Spell Trigger)
SPWI908 (Chain Contingency)
Also, it will be necessary to remove the following:
SPIN150 - SPIN157 (Shapechange subspells)
SPWI489 - SPWI499 (Polymorph Self subspells)
Note: opcode 172 functions at the moment as an "unmemorize one copy" effect unless one spell is memorized in which case it unmemorizes one copy and removes the spell from the spell book. You might need many instances of this effect for each spell (like 5 just in case).
Note2: If opcode 172 can be expanded to be able to "unmemorize" multiple copies in one go (with params 1 or 2) then that would be fantastic. This is somewhat relevant to this thread concerning 172: http://forum.baldursgate.com/discussion/35033/known-9861-creature-files-overriding-memorized-spells
EDIT: To clarify why removing shapechage/polymorph spells is a good idea is simply that they act as "temporary" spells which appear and disappear at duration end. However, as "temporary" spells, they are copied to the project image/simulacrum unlike temporary effects (with duration/delay) which are not copied.