If Bismuth is a very skilled blacksmith and Peridot can control metal and has serious tech skills, I wonder if they’ll team up to make weapons and such? Perhaps some giant mechs? That’d be really freaking cool.
I honestly think if they ever fused, the fusion would only be a bit better at battle than Bismuth with Peri’s powers, but she would be the QUEEN of inventions.
Need to repair a huge spaceship in freefall? She’s got this.
Invent some highly specific device? She’s got this.
Giant robot? ALL OVER IT.
Assistance in fighting a powerful foe? Well, she’ll do her best and be down for it, but she’d really be better at making a sick weapon for you to use against them.