We know that a foot fault is when your foot touches the baseline before you make contact with the ball. However, what if your feet are planted, and your toss meets or exceeds the baseline, forcing you to lean over the baseline with your body?
I couldn't find anything about this in the ITF/USTA Rules, and players very frequently have their body over the baseline. Take a look at this slo-mo video of Roger Federer serving. He (and most other pros) always lean slightly into their serve for the exact reason you specified. It's fair game as far as the rules are concerned.
What happened if the server, he toss the ball, then he let the ball bounce and catch with his racquet,, is this legal or legal? Fault?