I would like a large circular world, starting with a ocean biome and working outward in circles towards a hell biome. After the hell biome a void or ocean is sufficient. The current order I would the major circles to be in would be
0 Ocean
16 Beach
21 Jungle
6 Swampland
4 Forest
1 Plains
12 Ice Plains
5 Taiga
13 Ice Mountains
3 Extreme Hills
20 Extreme Hills Edge
2 Desert
8 Hell
9 Sky
Rivers would be nice, a biome relative would be better...
7 River
10 FrozenOcean
11 FrozenRiver
Also a couple random spots for this would be great....
14 Mushroom Island
15 Mushroom Island Shore
And since no one actually likes a flat world....
17 Desert Hills
18 Forest Hills
19 Taiga Hills
22 Jungle Hills
I would also like all generated structure to appear normally inside the circle of land.
As for size, a length of 500 for each major biome ring would be great. making the map about 6500 blocks in radius.
Would this be too big, or even feasible for you?