Be careful... Beta might be Yoshi's new trap for all Legacy players:

Your charge, in this cunning challenge, is to climb up 100 floors of a mob-infested Dalamud and defeat him/her/it... or else you cannot log out. (And yes, just as before, I'm making another direct and shameless reference to Sword Art Online's story).

Honestly though, I will like to have a vary varied mix of Legacy and new people from all over the world play the beta. The idea is sound... (provided I get to elbow my way in)... because the development team will be able to really test a variety of things all at the same time:

For instance, Legacy players can swiftly test end game content, battle dynamics, faithful treatment of mythos, transportation efficiency, stressing the network servers, gear/weapon systems...stuff like that.

New players can test exploration dynamics, tutorials efficiency, beginner's levels, inviting more friends to try this new MMO, adjustment + placement of mobs for low level areas, social/cultural interest (is the content exciting enough to make u play more than an hour a day?)

So yeah, a mix is definitely the way to go