-----------------------
If you have a difficult to reproduce problem with install-menu
-----------------------

# cp /usr/share/doc/menu/examples/cat /etc/menu-methods/ 
# update-menus
# bzip2 /tmp/menu-stdin
# tar -cvf /tmp/tar.tar /tmp/menu-stdin.bz2 #and any other interesting file
# uuencode /tmp/tar.tar /tmp/tar.tar | mail -s tar.tar joostje@cistron.nl

If you want to try out a menu-method yourselve several times
(with minor changes etc), you can use the /tmp/menu-stdin file
this way to start your menu-method without starting update-menus:

/etc/menu-methods/my_wm < /tmp/menu-stdin

-----------------------
buttonbars:
-----------------------
  
Yeah, something like a tak "buttonbarpriority=0--99" added to every
menuentry, where buttonbarpriority=0 means that this entry is absolutely
useless in the buttonbar, while buttonbarpriority=99 means that this
menuentry really should be in the buttonbar on every debian computer
(I'm assuming neighter priority will be used in reality, if this ever
is implemented).

Then the file /etc/menu-methods/menu.h could have something like
  buttonbarentries=8
in it, suggesting that menu should create buttonbar entries for the
8 highest priority buttonbar entries. (These numbers can then easily
be overruled in user files in ~/.menu-methods/* or whatever).

Thinking about this, this might actually be doable -- but I don't forsee
any spare time comming up in my life soon, so it will take some time

(note that the subject of buttonbars and menus has come up quite
frequently on debian-devel).