So I rolled the dice and tried this method yesterday afternoon. I took the aluminum tape off of my bed (grumbling while doing so because it took me a while to get it all on there at the right levels), cranked the heatbed temperature up to 100°C, left it there for about 4-5 hours, then turned everything off. When I checked the bed this morning, the warp was definitely more pronounced, perhaps 30-50% worse than before. As you say, this is hopefully as bad as it will ever get, plus I tend to work with PLA at lower heatbed temperatures (60-65°C), so it will be subjected to less stress. Now it’s time to put the tape back on, followed by tramming.