I don't see anything authorizing reruns on Friday. They are certainly a good idea if Saturday is predicted to be rained out, which probably means someone should actually change the rules to legalize them.
What the rules do envision is the case where prelims run on Saturday. So if you reroll on the same day as prelims, it counts as a prelim time, if you reroll on the same day as finals, it counts as a final time. But rerolls are always on the day originally scheduled as finals (i.e: Saturday). Extending this to allow Friday rerolls to count as prelim times seems reasonable. You may have entries that can't take a reroll on Friday, but can on Saturday (damage, injury, etc.) so the team should have the option to choose one or the other (knowing that if it chooses Saturday & rains out, it gets nothing).
The danger of allowing a speculative rerun and deciding after the fact if it counts or not is that if a team set a rerun time that was slower than its interfered-with time, it could argue at the judges meeting that "no really, we weren't interfered with, so our reroll should't count".
If I remember right, the order on Sunday in '99 was funny, because some Men's heats had run twice already (Friday & Saturday), and some had run not at all, and so the heats that hadn't started yet ran first on Sunday so they'd have any time at all? And then we ran out of time/interest in finishing the rest?