Interesting idea about limiting chain reorganizations. I wonder how that would work. New nodes can't really know how many blocks are there and how much the reorganization is happening, then again I am not sure how you would make sure that blocks are created periodically.
That is not a big problem - just look at the Nxt code how it's done. Chain reorganizations occur when there are two parallel chains, you are on "chain A" and suddenly your client detects a "chain B" with a higher "score" (in many PoS currencies that value is called "chain trust"). If the client comes into this situation, he simply must look if the last block that have both chains in common is more than e.g. 720 blocks "away" in the past. If yes, then it won't reorganize. The client will stay on the fork.
Now that could be undesirable, because a fork that normally would get "orphaned" could persist a long time because clients won't reorg. That is also why some dub the "reorg prohibition" a "dirty hack". But the answer to that is that such long forks normally only occur when someone is trying to attack. That's why "Economic Clustering" is used: This feature allows you to look fast if you are on the same chain than other nodes, for example, the exchange you use, or your friends. If nobody uses your fork, you cannot use your money on it. You would then abandon the fork on your own and start syncing the blockchain again.
It seems to me that if you want to be secure in PoS your node needs to be online all the time, you can't miss something, otherwise you are in trouble.
You are not necessarily in trouble, but you are vulnerable in this situation if you don't look on which other chain the other known nodes (exchanges, service providers) are. That is the main weakness of PoS. The well known blog post from Vitalik Buterin I already linked above explains it well.
In PoS you can create the whole 100 year history in just one second and two disagreeing blockchains would seem equally valid for a new node.
You would need a pretty big supercomputer to create a "100 year history in one second", but I get your point.
The "equally valid" does only hold true if both blockchains have exactly the same "score" which is very unlikely. Like in PoW, the "longest chain" wins - but in PoS, an attacker can re-create a "longest chain" with the well-known nothing-at-stake attacks, however, as already said, that's not trivial because he must obey the blockchain rules (he cannot create "stake" out of thin air, as long as he doesn't re-create the genesis block).
PoS seems to me like a very risky idea, it should definitely be more tested before it would be implemented in the biggest cryptocurrency.
Here I agree, as I already said. There is more research needed before implementing it in Bitcoin. I would also first implement a hybrid PoW/PoS version.
I didn't really refer to the ease of starting to use cryptocurrency, everything should be as easy to start to use as it can be. I was talking about the ease of getting power in the network. There shouldn't be any restrictions on your power in the network based on your time of adoption.
With the "reorg-prohibition" earlier described, "young" nodes have the same power than "old" nodes with the same stake.
Lightning is an off-chain transaction method. The only thing both have in common is that LN, on its own, doesn't require much additional electricity use. But LN needs a blockchain to work, and in the case of Bitcoin, a proof-of-work blockchain.
