The PID controller uses the Saturation block. If you don't want a Saturation block, or if your max and min are dynamic, you need to roll your own. The logic is something like,
This logic could be put in a subsystem using any of the following:
* relative operators & Switches
* relative operators, Enabled Subsystems, Merge
* if block, If-Action subsystems, Merge,
and then your subsystem could be a block in your custom library...you could find it useful again.