Debian first experience made a bit easier...

[Nikita V. Youshchenko]

> > That will result in two icons in launchers.
>
> why nor let the user decide on installation or check in postinst for arm
> and copy the matching one?

Not "for arm" but for "fso-controlled device".

And depending on a result of such a check, different .desktop files should 
be installed under /usr/share/applications/ ...  This looks more tricky 
and ugly for me than install-time-hook approach.

Anyway currently there are more urgent things to do :)