You have covered the topic very well. Another example to look at is the Kali applet:
http://www.scienceu.com/geometry/handson/kali/index.cgi?group=wt
For Tiling along the Path you could support the seven Frieze groups and for Rotational tiling you could support the Rosette groups.
In the guides for a given symmetry group, you could show the rotation points (along with their degree) as well as reflection lines, glide reflection lines and translation directions and lengths. I think you briefly describe these ideas in your document but since there is quite a lot going on here it may be useful to spell it out in detail for each symmetry group. The user should be able to move these guide lines and points as long as they stay within the constraints of the chosen symmetry group.
Below is a picture of guides for symmetry p6m (colours just used for visibility but should conform to guidelines elsewhere):
http://inkscape.13.n6.nabble.com/file/n4628619/wallpaper.png
The book "The Symmetry of Things" by Conway, Burgiel and Goodman-Straus has some very nice visualizations for reference.
-- View this message in context: http://inkscape.13.n6.nabble.com/New-tiling-interface-proposal-tp4570734p462... Sent from the Inkscape - Dev mailing list archive at Nabble.com.