Fascinating project Stroam. The term landmass would seem to involve oceans and seas I assume. That may lead to at least marginally smaller size world files, where compared to ones which record pure land with no seas.
Biomes is another issue, and I do not like the random patchwork of Minecraft at all. Obviously Biomes would sit atop landmass, but what they are and why they are there may be affected by factors that can be assumed to exist, through in actuality they do not (like wind and ocean currents). So if you can generate a Landmass map, an abstract overlay of winds and currents could dictate where and what types of biomes exist. It would also affect temperature. That sounds complicated, but it could provide a degree of pre-destination and certainty in the process of placing biomes. A draw back to that idea may be that it would means climatic areas are vast. But that does not mean climatic areas would be single biomes, because a large variance is possible in regions sharing the same latitude.
If you get around to generating polar regions, i would gladly contribute some templates for large scale ice formations.