When I played as Arabia I found solar panels extremely useless. It's a very late technology, and by that time the number of possible specialist slots are plenty and it never worth to work these tiles even in costs. So I guess solar plants should somehow turn more desirable to build. And about the swamp and rainforest/jungle, yes we can say that they aren't any good at the moment. The point is valid. But at least jungles can be cleared while swamps are always there which isn't realistic at all. I mean we have the technique to drain them if there's a will.