AverageBoss

It is an event happening next year. Every GA is getting one model for it.

Well again, you just deploy your army in a way where you finish one unit before your opponent. You minimize your opponents ability to react to your drops, and you get to decide turn order. It varies from book to book. It will be in the battalion rules in any given battletome that has them, before the battalion descriptions.

You don't ever roll to see who goes first on the first turn of the game. The player who finishes deploying first gets to choose turn order for that turn. 90% of the time it is better to choose to go second to give yourself the first double turn (if one happens), and put your opponent on the back foot waiting for it to happen. You can throw down your battalions in one drop (even if it is your whole army), or you can piecemeal them out. Once you do so however, you can only deploy remaining battalion units one at a time. So an eight unit battalion could be deployed all eight units at once, or four units -> one -> one -> one -> one, as an example. Because of that, you also don't get many opportunities to actually counter deploy large battalions. Your opponent will simply count up your number of drops, and deploy in a manner where they have one less drop than you. It is an extremely potent advantage.

There was also a multi month gap between Thousand Sons and DoT. When Nurgle Demons get new models is when you are more likely to get the double release.

Ya. Behemoth is the reason. But there are plastic kits that have been left out. No Dracoth lord for example, despite all 4 Dracoth riders, the chocobo lord, and chocobo riders being there. No Chaos Sorcerer Lord. No Ogroid, and hes a brand new plastic model.

No, he is far bigger. Ogres come on 40mm bases. He comes on a 60mm base.

The megaboss is in the official release.

It depends. If your models moved to larger bases, then you can snip off the bottom rim, and glue it to the top of the new base. Then you just need some extra flock. If they moved to smaller bases, that's much more of a problem. I personally am not going to bother. Daemon infantry have already switched bases twice during AoS and are pictured on both sized bases in their respective battle tomes (DoT and BoK). Whats more is I am pretty sure this: shows that GW only packs models with bases that accommodate their poses. Additionally, you still see space marine armies at GTs with sqaure based bikes and 25mm marines. I don't think AoS should be less inclusive to legacy armies than 40K.

Unless you are going multiple sizes in either direction, any difference is marginal at best. While smaller bases allow for one or two extra models to attack in close combat, larger bases provide more area denial, enhance the power of aura effects, and give you more options with anything that requires measuring range from the base. They went to 25 round at AoS launch, but the boxes as of DoT now come with 32s. Ask your local TO, but at the end of the day, you should be fine using whatever the models were packaged with.

Some LotR models are fantastic, and look much better than WH/AoS models you would be replacing. LotR eagles make great HE eagles. Ringwraiths make cool and varied wraiths (and they were actually bigger than the metal VC wraiths that existed at the time). Though that was better back when wraiths were units and not just characters. LotR bats look tons better than the actual VC bats. A fellbeast makes a good wyvern or dark dragon.