We're trying to create an square grid, icon-based menu that is permission trimmed (certain icons appear based on your specific SP permission group), that dynamically rearranges the icons based on your permissions. Our requirements dictate that we must avoid GAC-deployed solutions, so attempting to alter SPSecurityTrimmedControl to respond to SP Permissions groups (instead of levels) doesn't seem doable. We can achieve the desired hide effect using web part audiencing (we understand this is not true security, but it is sufficient for our needs).
Right now, to achieve the desired arrangement/treatment of icons we are placing each one individually in a web part, applying the audience, and placing all of the webparts in a horizontal web part zone. This method creates the desired behavior of sliding icons over to the left when one is hidden, however, we can't determine a way to limit the the width of the zone and force the icons to wrap to the next line so that they can move fluidly based on what's shown by permission group.
If we are barking up the wrong tree and there's a better idea, or any one has any thoughts on achieving this wrapping action, we'd really appreciate it!