Well I think your "hassle" suggestion is related to adding hot/cold water several times per day to adjust the temp variance... No way will I do this

Not that I dont like your suggestion but you are right, i'm not looking for a "hassle" like that and it would prompt me to purchase a fridge. I'm HOPEING and pretty much expecting very little variance in the temperature. Here are my thoughts on this:
--The garage has a concrete floor, this temperature probably remains fairly constant.
--It is protected from sunlight, wind, and other elements.
--A swimming pool does not vary temperature from day and night (in regards to ambiant temp, a heated pool may lose a lot of heat over the night, but a pool at ambiant temp will not change that drastically in 1-2 weeks time in a sheltered environment, thus quantity of water is really relavant to this project.
--I like the idea of insulating the top of the carboy... I actually have a big cooler made of stryrofoam that the carboy can sit in with water around it.
--I'm also thinking 1-2 foot plastic kiddie pool might work as it holds a lot of water.
My goal over the next few days is to get a glass of water to reach a stable temperature of 45-55 degree's, I will submerse this water in an aluminum trash can, hopefully the concrete floor will transfer its coolness through the trash can... if I can do this by Saturday, the project is a go!