I know I post alot of shit, but anyway I post this.
I think it would be cool if there was like an option before spawning(Or a button where the seeds normaly are) that if you clicked it, then a GUI screen would come up, en doing so, you could pick what biome you would spawn in, or certain traits and qualitys to the landscape, I guess you'd have to come up with a way where you store minecraft seeds and write a desc about it, I would like that mod, so I wouldn't end up spawning in some baron frozen landscape with nothing around me whilst trying to film or something like that. :D

Tally ho!

-Tom