Second, if you have a keyboard layout that is active, modify it (in Ukelele or any other way), save it, then log out and log in again, the system will not load the new version. You need to modify the folder that contains the keyboard layout to get the system to recognise the change. The easiest way is to drag the keyboard layout file to the desktop and then back to the Keyboard Layouts folder, then log out and log in again. Restarting will always load the newest version of a keyboard layout.
Any more sane method?
So it seems that most likely no. Here's a way to partially automate it with Applescript though:
do shell script "touch '/Library/Keyboard Layouts/'" tell application "System Events" try tell process "Ukelele" click menu bar 1's menu bar item "File"'s menu 1's menu item "Save" end tell end try log out end tell