Another instance of us being out of sync. Lets focus just on carapace and thorn to begin. As Carapace is currently written, they get points equal to their wisdom score to build a custom suit of armor that roughly falls in line with existing mundane armor. As Thorn is written, they get 1 + wisdom modifier points to build a custom weapon that roughly falls in line with existing mundane weapons. So at the end of the day, these abilities basically replicate core starting equipment.

If you are in agreement about what they currently do and the numbers (wis score & 1 + wis mod), the next step becomes deciding if there should be a built in scaling bonus and if so, what that should be. I had forgotten the initial suggestion because I was so focused on figuring out where we got off track. I think the scaling bonus idea is a good one. Your suggestion of 1/3 level would leave them at +6 over their career. Is your intention with that number for it to be just an enhancement bonus to hit/damage or is it tied to adding special abilities as well?

For my part, I think a standard enhancement bonus is good with some separate way to add cultivars, which will stand in for other effects. Then we can break down the weapon / armor enchantments and make a cultivar menagerie.

Ghost Orchid (+1 Thorn Cultivar):
When (entwined?), ghost orchids grant the Ghost Touch property.

Simple stat blocks like the above with fun names that reference plant themes or actual plants would be the idea. Mechanically, its just a cultivar that grants a specific +1 magical weapon special ability. There would be no cultivars adding just numerical enhancements. that would be covered completely by the built in scaling bonus.

What do you think about that?