1. A soft clipper plugin.
2. A downtempo plugin like fl studio´s gross beat plugin or halftime plugin by Cableguys.
3. A mastering plugin like a Maximizer, it's also a Compressor, Limiter, Noise Gate, Expander, Ducker and De-esser all in one for the soul purpose of mastering.
4. A linear eq plugin also for mastering.
5. Peak level display in the mixer.
6. I believe this would be a game changer if studio one has its of stock plugins i mentioned above.