Hey
New idea ... what about letting druids replace prepared spells with spells related to their environment. This idea would work somewhat similarly to the cleric's ability to convert prepared spells into cure/cause wounds spells, but with proximity to certain natural "nodes" or sources determining what spells can be converted. To do this, we take druid spells and divide them into a couple of categories. As an example, let's use Animal, Element, Plant, Weather, and Hex. Looking at just first level spells from the PH we get:
Animal: animal friendship, calm animals, invisibility to animals
Element: endure elements
Plant: entangle, goodberry, shillelagh
Weather: faerie fire, obscuring mist
Hex: cure light wounds, detect animals or plants, detect snares and pits, magic fang, pass without trace, summon nature's ally I
Now, a druid prepares any of those spells using his normal first level spell slots. However, whenever he nears a source (or node if you will) of that category he has the option of converting a prepared spell into a different spell from the category. The higher the spell level to be converted the greater the source must be, for example converting a prepared first level spell into animal friendship would require the presence of an animal (the druid's animal companion might suffice). Converting a ninth level prepared spell into shapechange (which I would peg as belonging in the Animal catregory) might require the proximity of an entire herd of large animals. Similarly converting a spell to an Element spell at higher levels might require a direct contact to an elemental plane.
The idea would be that zeroth and first level spells can be converted almost automatically (unless the druid is in some totally alien place without elements, weather, etc), second level spells slightly harder, third level harder still etc. until the conversion of a ninth level spell is near impossible.
The one exception to this would be the Hex spell category. This is basically the catch-all for spells that don't fit in the other categories. These spells can never be converted (though I was toying with the idea that Hex spells might require proximity to the druid's grove as a source). This category also contains some truly useful spells, so druids won't be able to steal the cleric's thunder by converting prepared spells into cure spells, or be able to convert up a dispel on the fly.
Here's an example first level druid named Goat with a Wisdom higher than 12. Goat prepares the following spells at the beginning of the day:
0th - detect magic, guidance, light
1st - cure light wounds, shillelagh
Later on that day Goat realizes he needs to sneak past a couple of guard dogs and could really use the invisibility to animals spell to aid him. He rummages around a bit and finds his animal companion ferret in his backpack. The proximity to the animal allows him to substitute a first level spell for another first level spell on the Animal list - among which is the spell invisibility to animals. Goat trades in his shillelagh spell for invisibility to animals (since cure light wounds can't be traded in for later - it's on the Hex list), stuffs the ferret back in his pack, casts the spell, and quietly walks past the dogs.
Comments, rants, flames?
-Matt
