The silicone (ACK!) is just for asthetic purposes. Once removed you may find the belly band is not perfectly aligned with the body in some places. Caulk helps with that by giving a finished look.
Removing the old caulk and replacing it would certainly be easier/faster than removing the belly band, grinding, fiberglassing, etc. Besides, I think a shined up band looks great! YMMV
Ten Forward - 2014 Escape 5.0 TA
Double Yolk - 1988 16' Scamp Deluxe