I often come up the situation that a couple of slices in my MBR disk need to be deleted and created afresh. Deleting the slices with gpart is not a problem, but recreating the two slices often leads to wrong partition order:
Slice 1 > Slice 4 -> Slice 2 -> Slice 3
gpart should have a fixorder subcommand to fix the partition order as:
Slice 1 > Slice 2 -> Slice 3 -> Slice 4
Linux fdisk has the ability, so gpart should as well.