VHDL Part 48 : Mask Generator, Third Solution

I cannot use the second solution. The problem with it is that the inputs have to be fixed. The mask generator that we want to do has to be flexible where  the components' ports and signals depend on the length of the input. My teammate will give me an input for the valid length then I plan to convert it to integer and use it as a parameter with which I will map my subblock generics. The problem is this method produced errors all have to do with the following:

The actual value [signal_name] associated with a generic must be a globally static expression.

I have to look for another way.