theEH,
A bit more plausible this time.
True, if a right handed batter walked in front of the catcher and interfered with his throw to second base there is the likelihood of an interference call.
Your second scenario, regarding the left handed batter heading toward first, would probably be a "had to be there" thing.
If the batter was only a few steps away and the catcher just drilled him with the ball I could actually lean toward calling the catcher for doing something malicious. On the other hand, if he was actually trying to pick off the runner at first and I judged that the batter hindered his attempt in any way, an interference call would be warranted.