As a GM, I would severely limit the more esoteric catches. Harry can't wrap sunlight into a handkerchief anymore after Susan becomes infected because he isn't happy. Bob mentions that there is no such thing as a "true love" potion, just some close approximations using lust. Both of these tell me that there is a strong spiritual component to esoteric catches that is wrapped up in the core of the character and not just the ingredients of a spell.
If you want "true love", you should be in love, or the person you are enchanting the item for should be.
If you want sunlight, you should be truly happy.
etc.
I have to agree with this to a certain extent. I'm not sure whoever is weilding the object needs those characteristics, though. It's not like a sword of the Cross that can only be weilded for its True Purpose. I do believe True Love/Happiness etc... has to be part of the ritual. Harry had to be happy because he was creating the potion.
For a ritual of true love, having a married couple willingly participate, or a mother who is trying to rescue her son from the White Court provide an important keepsake to the ritual would have to be part of the ritual. Once the ritual is complete, the object is imbued with the special property and anyone can use it (except WCVs of course).
I'm not a big fan of 'gem sitting in the sun for a week'.
It's the metaphysical weight of sunlight that is more important than a 'sunny day'. The Sun is the source of all life on earth. BCVs are the antithesis of life and this is why sunlight kills them.
The longest day of the year, the solstice is celebrated everywhere, it represents life, the planet is ideally placed and therefore, there is a lot of metaphysical weight doing it on that day. It can also only be done once a year.
If you want to put a gem in the sun for a week, then I'd say, what is that gem? Is it the birth stone belonging to the BC vampire you want to kill? A gem celebrating the birth of a person before it was a vampire - when it was alive and new. That has metaphysical weight.
The 'one week in the sun' is only cool if you have to spend a week of game-time trying to undo vampire shenanigans for the whole time until its ready. you know, if there is a time limit and waiting a week creates tension in the game.