if the idea is to give yourself multiple shots at a PR, and chase some rank or qualifying time, it won't happen. if you try hard the first heat first meet then you're gassed the rest. if you pace through the several races then none will be a PR either. you at best get one good shot with diminishing returns. if you need one good time find one good meet with fast opponents and go all-in on a single race. you don't get faster running more than once, this doesn't make sense.
now, if the idea is to do some sort of initial progression meet(s) where if you advance from that meet you can do something bigger this summer, that makes slightly more sense. you chase the progression placement each meet. you see what happens. you don't need a diminishing time so much as a placement a la the olympics.
that being said, if it's a progression concept, unless the second meet is easier to progress than the first, realistically, you still face an issue getting the job done. your legs will want to do less day 2. if day 2 is as hard or harder, your opponents will be rested, and you will be tired and asked more of. to be real, most college conferences will make you do heats like this. but people wouldn't expect 2 PRs from it. at most 1. they would either get their placement day 1 and shut down, or something like that.
personally unless day 2 is just a lot easier, i would pick one meet and go all-in on the time or placement you need. this isn't gambling, 2 chances aren't better than 1. my experience most of the time a full-gas heat time was better than i had left for a final. the second race you just go out and compete and forget about time. with all that implies for your theorized two bites at the apple.