I've always used in-accords for ornaments like this. It does seem a bit cumbersome when every measure has ornament options, but short of rewriting the whole aria a second time with the ornaments, this is the best way to present it. Besides, the singer may want to use some of the ornament options but not all. Rewriting the whole thing would make it more difficult to pick and choose their favorites.
I also think it's fairly concise and helpful to the singer - they can skip over the in-accords when they want to or refer to the optional melodic lines when they want to do that.
Hope that helps!