Changing Timing Cover with Engine in Car

Loosening the pan bolts runs the risk of introducing a new leak, unless you have the re-useable gasket.So no, I would not do that, and, really, there's no reason to.

Honestly, I had more problems with leaks when I didn't lower the pan, so seemed like the extra step was worth it. never had a oil pan leak. But maybe I'll try it your way again next time.