I did my version of the Minimig just for the fun of it (I have a fully working A500+ with all options on it but hardly use it due to lack on easy access to software/games) and also to be albe to use ADF-files directly. The possibility to use standard PS2 keyboard and mouse adds to it, VGA too (I added S-video and Composite too in my alternated design).
And finally - there are two things more: Nostalgia and "Because We Can..." ;-)