For the sky lands generation shouldn't it be faster if they switch to the cubic chunks system? It would allow it to go up forever which would cater certain fans a lot. To me if they do implant the cubic chunks system that would be the icing on the cake. I'd love it having options for max height and depth, and such.
I foresee a problem handling sky lighting; if your world is so high it can't load a high chunk that contains an obstruction, you'll still get your sunlight in the lower chunks.
One of the other things I wish 1.7 would modify is the horrible tall grass spam in the plains biome. Like the new temperature system but fore tall grass since it takes forever to clear it out even though I can insta-break it.
This is somewhat true, but without that grass the plains become dull and featureless. I think the solution here would be to add an "herbicide" which kills all tall grass within a specified radius.
Last thing but not least I wish they would add the unobtainable enchanted books (ones that you can't get from enchanting). I would like a regeneration enchantment for durability but it would be super rare. Since I burn through diamond armor and iron armour very very fast (every day or two) and unbreaking sadly doesn't help at all. Maybe an horse armor enchantment which is unobtainable too which spawns lili pads or ice under the horse but it could only be put on diamond horse armor and make it take durablity to balance it out?
Regeneration would have to have another adverse effect to make it not be overpowered. One was added in the Thaumcraft mod, which saps Vis from the local aura, but that's sort of irrelevant. Unbreaking works damn fine for me for the most part. Horse armor is a bit buggy as is, and the enchant you specify would have ALL SORTS of issues, namely use for griefing ocean-fortresses. Perhaps a "Water-walking" enchantment, but then because water can have different slopes and heights that wouldn't work very well either.
I've also thought of an idea for variety in biomes every time a biome generates it has a chance to spawn with certain stuff so you could see a mushroom forest to an forest with a mix of mushroms or none at all. Or a dead tree forest via no leaves it could even be integrated with the temperature system.
Biomes o Plenty and the Twilight Forest mod sort of do this; Mushroom Forest is included in Twilight Forest dimension, as well as a deep dense version, and Dead Forests are in BoP. Yes, I know you think BoP sucks because it doesn't "look or feel default". Tough.