First have a question related to your new scope and how you attach it to the head. Can you share some more information about what looks like a home-made attachment that replaces the CNC rings? Any idea about the weight? (Refer to attached picture, green arrow).
Next - I have been thinking about your concept. One idea I have is to design an add-on to a so-called "belly-boat". Just add a platform and a dome/camo net. The scope would be at ~20-25 cm above water level and needs to be operated through the LCD, which is not an issue as long as the distance to eye is comfortable. Not being constrained by water depth would be an advantage, and with flippers you can explore quite large areas. Launching and landing without putting the setup at risk might be a bit tricky though...