4) premined pos which saves energy
I don't understand that point. How does pre-mining save energy? What is "pos"?
I think the biggest single improvement to the Bitcoin protocol is changing the hashing algorithm to reduce the disadvantage of general purpose CPUs, so as to maximise the number of miners. Eg Litecoin.
Other than that, a coin would need a big backer. If a consortium of Amazon, Google and Microsoft all started promoting and accepting Litecoin, then I suspect focus would switch away from Bitcoin quite likely. I mention those companies because they all have server farms which they could potentially use for mining. And they are farms of of general purpose GPUs, not ASICs. They would be better at mining Litecoin than Bitcoin.
Perhaps another change would be to an inflationary policy. A lot of economists think a steady inflation rate of 1% or 2% is good for the economy, to stop people hoarding coins and to encourage investment. Without getting into the argument of whether they are right to think that, a new coin with such a policy hardwired might attract a lot of support in some circles.
Aside from that, and possibly even including that, I think Bitcoin is already so good that the "better" coins aren't sufficiently better to switch. Bitcoin has too much momentum. There's lots of venture capital going into Bitcoin. Litecoin already has several technical improvements, and it doesn't seem to be enough.
If miners can be encouraged to run SHA256 for something more profitable than Bitcoin then bitcoin will die quickly, it's a winner takes all game.
I don't follow. If some miners switch to a new coin, then the Bitcoin difficulty will drop and the remaining miners will make more coin. As long as the value of bitcoin doesn't crash, it will reach a new stable point with a lower number of miners. How is it "winner takes all"?
I dunno, ohhh.. lets say a government backed and regulated coin.
Which government? Do you think Europeans would be happy for their money to be regulated by America, or vice versa? Suppose Russia was the regulating government, and as part of their political argument about Ukraine they decided to black-list the coins of everyone who disageed with them? I'm British - would you trust the British government, given that in the past they used anti-terrorism laws to freeze Icelandic assets? (Hint: Iceland was not a terrorist country at the time.)
"Regulated" is a myth. It implies a central regulator, and that doesn't fit with a world currency - an internet currency.