FabFilter

For your next version of Pro-C, it would be great to have much more control over the transfer curve.

For dynamic sources like vocals, it makes a lot of sense to not just compress loud parts of the signal downward, but to compress quiet parts upward at the same time. That's why parallel compression and plugins like Waves MV2 are so popular.

Ideally, Pro-C would provide at least the same functionality of Kilohearts Dynamics, which lets you set two thresholds and adjust the transfer curve below the lower and above the upper threshold. Really great: kilohearts.com/products/dynamics

This enables all four types of compression (upward/downward compression/expansion) and, importantly, use them at the same time in one plugin instance.