Why don't we have more Ornn masterwork items?
Would it be too difficult to make them? I don't think so, because the only differences between them and their not-upgraded counterparts are the stats they give, their names and the border around their icons.
Would they be too hard to balance? Why would they be? There's already 8 of them, so their existence isn't problematic by itself, and adding new ones wouldn't change anything because you can only have 1 per champion.
Why do I think there should be more of them?
Because there are champions who can build none of the current 8 ones. Here's a couple of examples:
1-
: there are only 2 masterwork tank items,
and
. Zac can build neither the former, because he already has
as his mandatory jungle item, nor the latter, because he would waste all the gold value that went into the mana stat.
2-
: if I have to build on-hit because the enemy team is tanky, I won't be able to buy
, so I'll be left with no actually available options.
So, why doesn't Riot simply add more masterwork items to the game? Having too many would be better than having an insufficient amount, because at least players would have more freedom of choice when it comes to the bonus stats they give.


or 
would probably also be cool.
= pwn tanks.