A dozen metamagic cantrips (meta-cantrips?)

[coriolis]

I've used a similar idea in my campaign in conjunction with power components (http://www.d20srd.org/srd/variant/magic/metamagicComponents.htm#specificMetamagicComponents and also Ronin Arts' 101 Arcane Spell Components). Basically, you need to energize the component by casting a 0-level spell as a free action -- in effect, this limits the number of times per day a caster can use a power component to his number of 0-level slots (4 for wizards and 6 for other casters).

For a more restrictive rule, you could require one 0-level slot per metamagic level increase. I would reduce the cost of the components in that case.

 

[knight_isa]

I've used a similar idea in my campaign in conjunction with power components...

What level are your player's at? I looked at those when I get Unearthed Arcana, and thought they were outlandishly expensive. Just looking at acid arrow, you can add empowered for 1200gp. You could get a scroll of empowered acid arrow at 12th level for that price. Cheaper, if you're willing & able to scribe it yourself.

Of course, I generally play in the 5-10th level range. Maybe at higher levels things are different, but I'm not sure how they would be, since I think I'd rather carry around a sheet of paper than a pile of masterwork darts when both have more or less the same effect. Am I missing something?

 

[coriolis]

We're now (we rotate as DM) 15th-level, but we started using that rule at around level 10. The cost hasn't been too much of a problem, because most of the components were part of the treasure from enemy casters. Our sorcerer also has a high Craft (Alchemy), and so he's been able to make a few of the alchemical components (we also use the craft point rules from UA which helps timewise).

 

[Ilium]

Basically, you need to energize the component by casting a 0-level spell as a free action -- in effect, this limits the number of times per day a caster can use a power component to his number of 0-level slots (4 for wizards and 6 for other casters).

Of course a sorcerer can always use a 1st-level slot to cast that 0-level spell if they want to. But that can't be worthwhile very often.

Knight_isa: I really like this idea. It adds great flavor as well as being mechanically sound.