This would be my ideal implementation. Rather than the one-time all or nothing we have now, I would very much prefer to have to make a choice of which tiles I attempt to save, one at a time. This would mean you are still racing again the rising water levels, but you can save at least some of your key infrastructure. Which could lead to some tough decisions if you know you can only save one of multiple tiles before the levels rise. It would also tone down the Valetta bonus to not be so outrageous. Plus it would mean you would have a continual worry if levels continued to rise and you then later needed to try and save your 2m and 3m tiles. I don't think I've been able to save coast when it's been more than 2 tiles for a city. If it continues as is, I will likely not even bother with trying to save larger stretches of coast.