Overlapping Magic Systems

[bionova]

We know that Ruin and Preservation share a magic system in the form of metal-based Investing. We also know that Honor and Odium also share a storm/surge based Investment system. 

Given all of this, what's to say that an unnamed Shard(s) also use the same base for their systems of Investiture? For instance, what if Brandon unveiled an Allomancy that was compatible with Scaldrial's but used entirely different metals? (Something along the lines of burning Uranium leads to toxicity resistance or something )

[Weltall]

Magic systems aren't created intentionally by the Shards, though they can exercise a degree of control over a system once it's manifested.The magic is the result of an interaction between different factors including the nature of the planet that the Shard Invests (which can affect Focus and any significance to numbers) and the governing Intent. We know you can make different magic systems replicate the effects of other system to a greater or lesser extent, but not everything can be duplicated in every system and trying to do so can lead to weird results. Like Nightblood.

So basically, another Shard isn't going to create a new form of allomancy unless a lot of factors happened to line up, in which case such a thing might be theoretically possible but vanishingly unlikely. Particularly from a meta standpoint as duplicating an existing system with a new Shard wouldn't be very interesting from a storytelling perspective. Especially not when there are so many other things Brandon can and will still do with the Metallic Arts.