And longest chain is a rule set by nodes, correct? Meaning, that consensus is formed by the highest voting number of nodes, in this scenario, my 2000 nodes.

If we go by the standard 6 confirmations, 6 depths, then we can safely assume it will be the longest chain. So after my 2000 nodes vote for a 200MB block, I wait 1h for the longest chain to become 200MB. Or for the real paranoid, we wait 2 hours, and I am certain that the 200MB rule is enforced and that there is probably not another chain.

I then spam it with 200MB data, and thus we get 200MB blocks until someone can form a better consensus (launch more nodes with a different blocksize consensus).

All this, I can do in less than one day, and cripple the network for less than $5000.

The majority of nodes decide the consensus, and the miners produce the actual blocks.

If the mining majority does not produce 200MB blocks, then eventually they will outproduce your chain, even if your 2000 nodes (not the majority of nodes currently, btw.) accepted it.

The only situation in which your scenario holds is if you control the mining majority and the majority of nodes.
Then you can maintain a longest chain with 200MB blocks (provided you generate the transactions to fill it).

If you can do that for $5000 then you can do it today already, nothing would be stopping you.

I don't consider it fruitful to continue this line of thought since it does not add any new attack that could not have been done in the past.

My initial reaction is that I don't think its a good idea to empower non-technical people with the ability to control such an important variable with a click of a button. I suppose they would be held into account by the miners and this would essentially be a node vote which would allow individual nodes to confirm larger blocks easier. The difference may not be significant as an attacker isn't going to be limited by the code and this could be a signal to allow users to vote. This change appears to me to have more political implications than anything.  

I am amiss to what that "1%" cited  difference actually is. Any hints?

Nodes will then have to follow the rules ascribed by miners, and their vote is pointless as consensus is formed by those who mine. Which means, Adam will still get kicked off the network, when the winning miners decide on 2MB blocks, and Adam only accepts 1.1MB.

You go wrong in thinking that miners are all-important. I clearly stated "the majority of nodes decide the consensus", not only miners.

As other have stated multiple times in this thread, miners have to be sensitive to where the real money comes from, ultimately.
As such, the "vote" expressed by BU nodes through the settings they choose to run, is an important piece of information to miners.
It is certainly not pointless. It would be pointless to ignore it, as a miner.

I still am curious as to what the difference is besides the nodes being able to signal to the ecosystem in a slightly easier way through a GUI that they wish larger blocks. Is this it?

I think there are a lot of misunderstandings about BU. The main idea is dirt simple:

• Current situation: blocksize cap for the network is set by miners/nodes converging on either Core, XT or something else by downloading and running Core, XT, etc.
• With user-selectable blocksize cap: blocksize cap for the network is set by miners/nodes converging on either Core settings, XT settings (BIP101), or some other Schelling point by adjusting their settings to do so (BU can be made to default to Core settings, if you want)

There's another "oversized block acceptance depth" feature LovelyDay mentioned that is envisioned may come in handy, but it can be turned off anyway so I'll focus on just the "user-selectable blocksize cap" aspect. This is all it is.

Why do you believe that miners are really that stupid?