No Star Wars Disney+ fatigue here. "I could do this all day long"....sorry wrong franchise.
The only potential risk I see is too much Tatooine if Obi-Wan and Mandalorian spend too much time there, and we would have say both running close to each other. Not sure if that would happen. Potentially Season 3 of Mando, but then they would probably be aired at different times in the year I imagine.
However I imagine Cassian will be set in a totally different part of the galaxy. The first thing that comes to mind are cities similar to the opening scene of Rogue One where shoots that guy in the back / street. That should make it totally different, but still the dirty lived in Star Wars aesthetic I love so much.
I read somewhere someone mentioned Obi Wan may only be 4 episode season. I hope not. That would surely be too short. The fans would probably rebel