Enhance Guides New and Guides New Percent
Add options to the Image/Guides/New Guide By Percent... and Image/Guides/New Guide... scripts to give the following possible settings:
Horizontal
Vertical
Both axes
Horizontal mirrored
Vertical mirrored
Both axes mirrored
Horizontal repeating
Vertical repeating
Both axes repeating
Horizontal repeating including 0
Vertical repeating including 0
Both axes repeating including 0
The first two options are simply what the existing scripts provide.
The "Both axes" option with a value of 50% (for example) would give centre lines.
The mirrored options would add two guides per selected axis. For example selecting "Both axes mirrored" with a value of 33.3% would give 'rule of thirds' guides in one operation, rather than the 4 needed currently.
Selecting one of the first three repeating options with a value of 30% (for example) would give guides at 30, 60 and 90%.
Selecting one of the final three repeating options with a value of 30% (for example) would give guides at 0, 30, 60 and 90%.