Hi All,
I was originally going to do a multi-quote, but that would have been a large amount of text to reference, and so I will try to address everyone's different points raised since my last post in a single post.
ORISONS: First, to state that "Orisons" are simply the divine equivalent of arcane "Cantrips". i.e. They are 0th level divine prayers as opposed to 0th level arcane spells. As such, orisons follow the same rules as cantrips: Can be cast without book or ingredients ... and (if I recall correctly) can also be learned without books as they are the very basic spells that can always be learned.
SABRANIC: You asked for more thoughts and feedback.
I have played PnP D&D since 1981 1st edition, followed by 2nd and 3rd and 3.5 editions. I embraced the move towards NWN\NWN2 computer aided systems, except they (in my opinion) lacked some "core" gaming aspects that needed to be addressed. However, let me give you some "gaming" feedback from my PnP years that may shed some light on my reasoning for you:
In the early days, there was no such thing as cleric "spontaneous" casting, but our group (under my DMing) ended up using exactly the same concept even before it had been given this name. i.e. A cleric could sacrifice a spell to empower a healing instead. Why? Because otherwise all a player would do would be to learn every healing spell they could and only rest/learn another spell if they needed it ... and exactly the same thing tends to happen with respect to other spell classes. i.e. Magic Missile for 1st level and Fireball for 3rd level, etc.
Basically, in this sense, the system is "broken" ... but that is how it was designed to work, and does work better in a PNP environment where resting and events are more controlled. However, in a CRPG environment, this kind of system shows its flaws more readily.
Now, I do have total sympathy for people like Tchos who may have the imagination and time to work with such a system, but I am also a pragmatist who recognises the pointlessness of over-exacting certain aspects of a magic system because that is how it was originally designed.
To continue my point, in our own PnP group, we eventually came up with the magical "Ingredients Pouch", which allowed the spontaneous creation of spell components for spells that required them (apart from anything too valuable, like diamonds) to help alleviate the issue of having to have certain items just to be able to cast the spell, which (and here is the point) ... that they may have the opportunity to cast at some time in the game.
The point being, players are reluctant enough to "learn" other spells that they *may* find a use for, when they may as well learn a spell like Magic Missile, which they are almost certainly going to use. Why take time to learn "Magic Aura" rather than "Magic Missile", unless there is a specific situation when and where you need to? And now if the player decides that this would be a good time to have and use such a spell, the game either has to take a step to one side and do something else (if it is that flexible) or grind to a halt as the wizard rests and learns a whole new set of spells just to cast Magic Aura in this unusual situation ... and then, the wizard may need to take more rest just to restock on their Magic Missile again (especially at low level).
The bottom line, the system is (if anything) already too inflexible to be fun (or practical) to play at the same pace as the rest of the game. And for this reason, is also why our own PnP sessions ended up developing a token system, which actually meant players did not even have to stipulate which spells they learned at the start of the day, simply because of this "wrong spell/stop/rest/learn correct spell" process that spoiled the natural flow of the game. Add to that the need for ingredients as well, and the problem just felt magnified.
Now, that all said, I do believe there is room for a combination of systems that does work well: The main problem (as I see it) is the issue related to role-play type spells, which rarely get used in any given session. I believe these are what a DM (or builder) should make the player work for as you (and perhaps Tchos?) put it. I certainly DO see the *fun* in this aspect of making a player work for their "spell". (I have an example in my module if you get the chance to play it.) However, those spells or prayers that are used regularly should not be reworked to add further difficulties to use them in the first place. (As an aside, you will probably find that most of the spells that require ingredients are usually the role-play types anyway.)
Furthermore, to help encourage the player to actually memorize different spells, I have also developed another system (which I have brought over to NWN, and works quite well), which is a kind of "spontaneous casting" system for wizards .... but only for the more readily memorised spells like Magic Missile. e.g. The system is called "Arcaene Lore" which comprises of spell scrolls that work with ancient power. In practice, if a wizard class PC found an Arcaene Lore spell (of Magic Missile), then they can quick slot it and use it to cast a Magic Missile, BUT only if they have a first level spell memorized to empower it.
Now, by such a system (and some other spells like this), it frees the player to consider memorizing some other spells that they may not have considered to do so before, due to lack of confidence to do so. e.g. If they can always cast Magic Missile from the Arcaene Lore scroll, then they may as well consider memorizing some other first level spells instead.
FLEXIBILITY: The great advantage of such a system is giving the player flexibility, but also within limitations based upon their abilities in the first place and the environment conditions in which they can regain their powers. By all means keep the "ingredients" for "spells" outside the normal ones a PC can learn, and perhaps stress the PC via their environment rather than their spell abilities due to lack of ingredients (apart from the very basic "tools of the trade" such as the "books" in the first place, which are not unlike the fighter's weapon! No weapon, limited combat! No book, limited spells!)
There is more I can probably add, but that may help give some background guidance for now (from *many* years of experience). 
Cheers,
Lance.