At Banno, I was given the responsibility of creating an entire custom iconography set, including solid and outline versions of each icon. Banno is part of Jack Henry & Associates, and is a digital banking solution that features both enterprise tools for financial institutions as well as consumer facing web and native apps. Banno's old iconography was a mix of Google's Material icons for the enterprise and an older custom set for the apps. The inconsistencies in these designs created a divide in the look and feel, and each set had smaller problems of its own (Material icons lack personality at large sizes, for example).
Keeping this in mind, I designed 240 icons at 24px. Solid icons feature sharper edges where possible and use a 2px stroke throughout. Outline icons were designed with a 3px stroke at @2x and scaled down. Outline icons were rounded and softened and given more personality for larger sizes, while keeping the overall metaphors similar between sets.