Hussar
Legend
Let's scale that back to "Very few will ever memorize Illusory Script before Fireball." because I know people who will....like me.
Really? Your 5th level wizard, with 1 (or maybe 2 depending on edition) 3rd level spell per day, will, without prior knowledge of what he will need, memorize illusory script before fireball?
Honestly?
Your group is the weirdest bloody thing I've ever heard of. If I did that with a wizard, the rest of the players would beat me senseless for being so useless.
So, I have to ask, why? Why, unless you knew beforehand that you would need this spell, would you ever memorize a spell that lets you write in code before fireball? And, really, why wouldn't you just... oh, I don't know... write in code?
I've never even seen this spell used by a player, let alone memorized before general purpose spells.
Janx- we did the same thing with clerics in our 2e games. It worked great actually. Granted, in 2e, clerics didn't have quite so many offensive power spells as they do in 3e, so, it might be a bit more problematic there, but, my experience mirrored yours. Having free rein meant that all sorts of spells got cast (including Snakes to Sticks - the only time I ever saw that one) cast that I never saw before.
Which rolls me back to why I think the sorcerer and favored souls work better. I'd say they need a few more Spells Known, but, honestly, not that many. And, if you gave them basic powers that let them attack, then spells could be reserved for actual effects, rather than just damage dealing.
Sort of combine the 3e warlock with the sorcerer and having at-will combat spells, and then Spells Known for the rest.