The Panasonic HCV-700

is on the mid-range of consumer camcorders.

The single 1/2.33" CMOS imaging chip is an OK size - but the 46mm lens filter diameter is on the small side. This means not much light will get into the camcorder for the imaging chip to deal with, resulting in the poor low-light behavior you experienced.

You might be able to open the aperture a bit more, but this could result in the shutter speed slowing and result in "ghosting". How to do this using the options in the camcorder's menu will be in the camcorder manual. If you do not have the manual, download it from Panasonic
http://service.us.panasonic.com/OPERMANPDF/HCV700-MUL.PDF

If good low-light performance is your main requirement, then you need a camcorder with a larger lens diameter to let more light in. My Sony HDR-FX1 and HDR-FX1000 have a 72mm lens diameter and large 3CCD and 3CMOS imaging chips, respectively, and they do great in low-light at clubs. As you have discovered, ANY camcorder can do well in daylight... You will notice that as the lenses and imaging chips get bigger, the cost of the camcorder goes up.

The only "camcorder modification" I can think of would be to add a video light. Since the HCV-700 has no accessory shoe, you need to add one with a camera bracket like
http://www.bhphotovideo.com/c/product/734090-REG/Vello_CB_500_CB_500_Dual_Shoe_Bracket.html
along with a video light like
http://www.bhphotovideo.com/c/product/743442-REG/Bescor_LED_70_LED_70_Dimmable_70W_Video.html
The "throw" of this particular light is probably useful to about 15 feet, so if that is not enough, you'll need a different (brighter) light.

I have found that the club environment can result in recording fast action. It is too bad that you decided to get an AVCHD compression camcorder for this. Fast action and video compression don't get along very well. I suggest you always record in 1920x1080/60p or HA mode as this should help limit the compression artifact issues.