I'm sure there's another way to look at things as well if they did start with the Arland trilogy. If a physical release of one of the games that's already been released on multiple systems and had multiple versions, is able to sell out, all the others should as well. If LRG is willing to take the greater risk with their endeavor and it pays off, that would look better to other companies and Koei, than something with a much smaller amount of risk. At the end of the day, we'd still likely see Ayesha and the others if Rorona did well, it would just take longer for them to come out.
I understand that Atelier fans probably have their own different favorite that they'd like to see released first, but at the end of the day, this is being used as a guinea pig to see if larger ventures are worth going after. If all they're going to do is try for safe bets, that doesn't really show anyone anything, when it comes to catching the big boys attention.