Considering GPP has tiny bodies up to 6 times further out than Eeloo, this works surprisingly well. A simple 'body discovered' popup would fix people overlooking the nice flavortext you've provided in the UI window, cause most people using this mod are going to be mashing the button at first. I personally like how distant bodies were harder to find- I was considering launching a telescope into deep space for a while there, which seems like a realistic and natural gradation of difficulty.
As far as keeping the bodies completely invisible until discovered, I like the idea a lot. Maybe bodies within a certain distance of your home planet should appear in the tracking station, but for further out bodies, you should have to put a telescope in a low solar orbit and run a different type of scan to make them appear? Getting close to the sun, and looking for moving reflections further out, since being in a low solar orbit guarantees distant bodies are illuminated, is the idea.
Another change I'd recommend, if you're so inclined- researching bodies at the space station seems too easy, just throwing funds at each stage of the research program. Depending on your mod set and where you are in career, you could have orders of magnitude more money than required. Perhaps make each phase of research take a week or a month or something, so if feels more rewarding, and like some research program is actually going on behind the covers.
Anyways, I absolutely love this mod. It made being in a strange solar system much more exciting, learning about the bodies in degrees feels much more thrilling than being able to immediately see them all and plan out your mission parameters decades before you have the tech to get there. If you got it up to full working order, I'd say Research Bodies is essential to playing in any Kopernicus modded system. Amazing how simple gameplay mods like this can change the experience so much.