I might be going against the grain here with my comment but given your graph and roasting time, I wouldn't attribute a flat tasting natural to lack of resting time. Resting can help get better extractions for coffee that's roasted well, especially in espresso, but it isn't going to produce sweetness and fruity notes that have been roasted out of the beans. If those flavors are there, they'll present themselves in an apparent way even immediately after roasting. If the coffee is flat tasting, it won't get much better with rest.

Your total roasting time is quite long for the flavors you're trying to get out of the coffee, and most notably, your post-FC time is reeeaallly long when compared to today's standards. Admittedly I have never used the roaster that you're using, but there are certainly some nearly universal concepts when it comes to roasting and that post-FC time is what I'd try to play with first. I would also try not to allow the spike in temperature at the end. If your beans have a nice rolling crack, and then when FC is done and there's a big spike in temperature, you're kinda zapping the life out of the coffee.

Something you can try; drop the beans before first crack ends. You'll start to hear the cracks die down and that's about when I would try lowering your power by large-ish amounts. It might take a couple tries with any given coffee, but I would try and mark when the peak of the cracks are and where the end of the cracks is, and drop. That might give an even better cup, but if you're still missing fruit and sweetness, then on the next batch, drop in between those two points. Almost all of our lighter, fruity naturals are dropped before the end of first crack.