I like that. I was thinking if I did myself as a Dino, which would be both neat and would remove the physical problems I'd have in rping, maybe a pterosaur type, their adult size isn't to large, not like a long neck anyway. Or a teenager if that is proffered by the gm.
If some want to be themselves as humans maybe something about the wish to be in the great valley, ect, worked with the person's inner wish or desire during the transfer or something to explain why some are this or that physical age, some are dinos, some humans, ect.
Like with me for example, can't run but a block, can only eat 3 things due to intestinal problems so would not have much fun in the great valley, I like dragons, dinos, & orcas so maybe part of the reason for the change to a dino body. Someone else may have an inner vision, or preference, if I were in the great valley I think it would be neat to be ... so that may be the reason they changed to that form. Even if they didn't give it much conscious thought, just a sort of flash thought in the back of their minds the wish may find it there.
Maybe crazy but just some ideas I had.