Its usually people making parts that seem to cheat instead of actually trying to use existing parts. On the other hand 3d printing masks is awesome, theres many masks we never actually got in set form or others which were weird like the Inika masks, I’ve seen them 3d printed for regular metru heads.
I agree with @AwesomeJoel27. The hands and torsos are meh, but the masks look really amazing! It gives you more of a variety than just the standard masks of the Toa.
I don’t see anything wrong with making “illegal” parts–most of them are either too specialized for LEGO to make or are parts they simply never will make because they can use other parts in a similar way. Why is it wrong to use your skill to make a part that accomplishes your creative vision? So long as you don’t try to sell it as a LEGO product, you’re not doing anything wrong, IMO.
I really want to buy a few of those masks. The designers do a great job, and they let you do almost anything you want!