Unless you use dsPIC you have to use digital anyway so that's fixed.
This is doable but has to be done in stages.
1. You have to convert the incoming frequency into a number, you can measure the frequency using a timer module.
2. I assume with your example of 2.2 gain means you are using an analog control signal so you have to digitize it into a number using an ADC.
3. Do some math on the two numbers to calculate the divisor needed to create the output frequency
4. Use another timer module or software to create the output frequency.
You may not be able to create every frequency using only a PIC because of the integer nature of the timer values but for low frequencies it should work quite well.
Brian.