Hi Pilou - it looks like you answered the question yourself!

Yes - the align command can be made to work in a specific direction by using the View > Cplane command to set the cplane to the orientation that you want.

So that provides a method to make that happen, without needing a special extra menu command.

It tends to be a good thing to reduce the number of commands in the menu, because pretty soon having some hundreds of items in menus tends to make things cluttered and more difficult to use.

I have thought before about maybe having some option in Align to take on the orientation of a line that you are snapping on to though, although possibly only if you are aligning a set of points and not entire objects.

- Michael