I just want to know your professional thoughts on my first implementation of a (slightly) complex PID control as a possible solution to a requirement of controlling a tank level, at the same time, the ratio of it's two inlet flow.

Please see the attached file for my (i know I can do better, but please forgive me for now!) sketch of the simple problem, as well as my proposed solution, through Cascade and Ratio Control Strategy.

I think this can be simpler (without cascade, just divide the output of the Level controller into the SP ratio, then send to the two valves), but I also think this proposed solution has it's merit while being more complex (the advantage of cascade control, the possibility of independent flow control, etc.), but I can probably be wrong, or missing something, for, as I've said, this is my first implementation, so please help me.

I would greatly appreciate any response, especially a quick one, for I need this to implement very soon.

Thanks much!