Scheels has a Vortex Diamondback scope for $99 that would be perfect for you
Would love to hear more about the process to make this work, if you got time to explain. I have both a kuiu and exo pack. Do prefer the Kuiu bag over the exo for some features and functionallyGo Exo.
Edit:
For the frame. I love Kuiu bags. The Kuiu bags can be adapted to the K4 frame.