If you want something for alternate tunings that can remain playable when down-tuned I would recommend you get something that has some sort of reinforcement in the neck, such as Graphite, Titanium, or Carbon fiber.
Others options are something with a roasted neck or quartersawn neck, which tend to also be stiffer than ordinary necks.
The stiffer the neck, the easier it will be to down-tune w/o making the instrument unstable to play.