Responding to HUARGH's suggestions, since some of them are very interesting, but maybe with a more... realistic perspective to some of them. I'll just bold the topics because I'll be going through them in a different order than he listed (based generally on how much I agree with them) and I don't want to insert a bunch of small quotes with a bunch of small responses. So...
More Pokemon per Team: I think there was an "Other Metagame" created for this, but don't expect this to become the standard. Looking realistically, Game Freak has based this entire franchise around a team of 6 Pokemon, and while the increased number of threats makes 6 too small to effectively cover everything, going against it changes something so fundamental to the franchise. Not being a "nostalgiafag", just looking realistically at what Gen VI would bring.
New Defensive Type: First off, while there is some typing imbalance, there needs to be some sort of logic when a new type is created. Dragons are meant to be mythical, ultra-powerful Pokemon, so nothing is realistically going to be immune to their attacks. You might be able to create a new type that resists Dragon, or alter the previous type chart to slightly nerf it (say, Ice now resists Dragon). While changes and additions to the type chart are certainly possible and may balance out some of the kinks they currently have, there must be some sense of logic to those changes, or Pokemon will lose legitimacy among the general public who makes up the bulk of the game's consumption.
Adjusting Secondary Effects: The concept behind your suggestion was interesting, I think the execution goes a little too far. Again, looking realistically, something that resists a move still takes damage, so he still is hurt by the move. That said, if he is hurt less, wouldn't it make sense if he was less afflicted by the secondary effect? I think making the secondary affect chance somewhat proportional to the type effectiveness can make logical sense, and I would support it being implemented in the game. There is an issue with Scizor being 100% burned by Lava Plume that way, but if he doesn't die to Lava Plume something's wrong with the attacker. Maybe capping both ends at a factor of 2 (1/2 chance if resist, double chance if weak). It gives an incentive to switching out of a super-effective move because you would now be more vulnerable to a crippling effect by staying in, while making a smart switch-in less vulnerable to hax.
No Team Preview: Personally split on this one. One one hand, given that the only Team Preview we have in game is by looking up a guide (I'm pretty sure stuff like the World Tournament doesn't have it), it would make sense if multiplayer matches re-accepted this trait as well. That said, Game Freak isn't going to rush to undo this recently added trait. I personally think lead matchups are not the reason why TP is seen as "bad". Yes, some leads are now unviable, but if your lead has a bad matchup against another lead, then you still have a chance of starting out on the right foot. Previously, if your lead beat 80% of the common leads in the metagame, you started out the match behind if the opponent just so happened to carry one of the 20% that beat you, something completely out of your control. I believe equally well-constructed teams should start out on even footing, something that TP provides in a limited sense. However, what may totally overshadow the lead aspect of TP is that it virtually eliminates the need to scout. TP now lets you see what strategies you opponent is likely to run, like playing a poker hand with the cards face-up. Concealing information is a good part of many strategy based games, and if I could choose I would probably choose no TP, but I don't choose so I can only cross my fingers.
Stealth Rock Revamp: A touchy subject for me, because Rocks are such an interesting concept. That said, there are some limitation to what we can logically expect to change from it. First, eliminating weaknesses to it won't happen. If something is attacked by rocks switching in, is there really that much of a difference to being attacked by rocks from a Rock-type? If there is, I would say that 4x weaknesses/resistances go to 2x weak/resist (so 1/16th, 1/8th, and 1/4th as the only damage options). I do like that anti-air option though, but I can't truly judge whether that 1/4th still neuters those Pokemon that much. I also think a "hazard counter" could be implemented, so you can say have Rocks as they are, but not Rocks and Spikes and/or TSpikes. This could technically allow them to introduce new hazards like the anti-steel ones people are mentioning (granted, I see Stealth Fighting as more realistic than Stealth Fire, just saying), without being too hazard-centric.
VoltTurn Revamp: Short answer: pick one. Picking the new switch in before the attack makes perfect sense, so you don't have the option of doing damage and being guaranteed an advantage on a virtual double-switch. You can also make them do less damage, say 40-50 BP. This allows advantageous matchups to potentially keep a Sub up, or not be put in range for an easy KO by a more shaky check if you don't resist it. A much softer nerf, but still could be effective. And make sure its general damage, not just against Subs, mainly because that's too specific of a change to logically expect Game Freak to make (let's make Subs have more defense only against these two moves doesn't make a lot of sense when you think about it).
Rapid Spin and Spinblocking: I agree on wanting another, different-typed Rapid Spin. Given how entry hazards were made more diverse in Gen IV, it would make sense that getting rid of them would become more diverse as well. Perhaps a non-damaging one that always works except when Taunted, an Electric/Ground/Psychic one that opens up some new spinblocking types. I might say that this topic makes more sense for a Substitute buff than VoltTurn, since Subs generally block secondary effects anyway (think Dragon Tail vs. Roar). Logically makes sense to make this field more diverse, but not necessarily high on my priorities list.
Status Moves: Yes, with status being an important part of the game, it's unfortunate that arguably the second most gamebreaking one (Sleep) has a 100% accurate move for it. Upping WoW's accuracy would help defend against physical attackers just a little bit better, and when Toxic is used it's generally considered bad hax if it misses. Maybe a 100% accurate burn move as a signature move on a new legendary is another option, but that's getting more into speculation.
Sleep: At the very least, Rest should not reset when you switch. If we assume the period that a Pokemon can Rest is finite, then there's no reason to have any loophole that can prolong it indefinitely. I wouldn't mind the entire Sleep mechanics to go back to Gen IV, but at the very least don't extend it to Rest users. I think a Spored Pokemon can wake up the first turn its brought back in, so why would it make sense for Rest users to not be able to do that?
Weather Nerf: I, and likely many others, agree with just about everything you said here. More viable Cloud Nine users for sure, that's probably the least Game Freak could do for us. Setting Drizzle/etc to 8 turns is what I initially thought of, since it is possible to successfully run Damp Rock rain teams in lower tiers. Maybe holding the weather rocks increases the duration to 12 turns. Still gives people an advantage for using weather, but not so much that they can just sac the weather setter against weatherless teams. Also agree with the power nerf. Just about every ability/item increases attack power by a maximum of 20% if there's no drawbacks (not counting Huge/Pure Power and Thick Club). Giving a 30% boost, essentially a Life Orb boost, is still significant without being able to necessarily power through absolutely everything in its path that isn't immune. And obviously Hail is currently so far behind everything else right now so a buff to counteract Rain and Sun nerfs (Sand I don't know what to do with) would be great.
tl;dr Umm... look for the most interesting bolded portion for you and just read that. Too many different topics to summarize completely.