First, all you are remembering an ANALOG system as to the leveling control. It's a piece of cake to do a quality job of this in analog circuitry for peanuts cost.
Second, to do this at HIGH QUALITY in DIGITAL is another story. It requires both AGC (Automatic Gain Control) and Compression Limiting to make this work right.
THIRD... we are looking at enhancing Hoster to do llive effects. IF... and I do mean IF... we accomplish this without spending tens of thousands of $$$, we'll consider adding it. Then, we could add what you are talking about. However, will it work with Keychnage? Or recording and mixing? Or vocal reduction? Probably not unless you have a 3GHz processor with 2GB RAM, and maybe not even then.
Live effects is a very complex issue... especially on a $199 product! 
As Forest Gump said; "That's all I gotta say about that."
