1) It would be interesting if Natures could also be set to act as strengths/weaknesses in themselves- for example, a Pit Fiend in a demon story might by its Nature have the Strength "Unholy Strength" AND the weakness "Inhumanly Ugly"

2) In addition to, or instead of the above: Allow Natures to be used as hidden gates versus certain Obstacles or Characters. The above fiend could, through some sort of scripting, find its Nature a weakness against an Exalted Battle Nun for example. Such a gate would be bidden in the NPC card in a format something like

<weak> Nature==Pit Fiend

This could also carry to Assets- a Troll could easily use a pair of Big Boots of Buttstomping, but might find it hard to wield a Pixie Toothpick Sword. So the PTS card might read somewhere in its gating

<AssetPickUp> Nature!==Troll

Please note I'm pulling this code out of my hip pocket, just for examples.

3)It might be nice to allow Narrators to set the number of different Str/Weak players have at the start, and/or assign assets to character at game start. For a superhero or Ultratech setting, for example, having a single strength feels a bit restrictive. By the same reasoning, allow the narrator, if (s)he wishes, to allow more than 3 in play at once (though this could lead to 'power creep', I think the extended narrative possibilities warrant it)

Allowing asset assignment at gamestart would bypass some of this, for example giving your Mage a Xappy Stick to xap with right at first, or your Xenomarine a suit of Xenocidal Power Armor.

All of this is clearly long-term thinking, not "ZOMG, we need tis NAO!"