One-second transactions
Bitcoin already has one second transactions, but it takes longer than one second to make sure no one is using 2 wallets in different locations for example to try and buy two different things with the same money. (Think of it as having a copy of your VISA card, taking it to two different stores and maxing it out at the exact same time. With a window of only 1 second, it'd probably be possible to rip one of those stores off).
Dynamic difficulty (readjusts every block)
Bitcoin already has dynamic difficulty, but it's hard to get a good average of how things are moving just by a single block. It'd be like trying to gauge how fast a car is going by taking just one picture of it. When the financial stake of all bitcoin holders is in play, a longer difficulty readjustment time is probably better.
A way to reclaim lost coins (No transactions for 365 days, coins start to trickle out of your account back into blocks at a slow rate)
This is a controversial subject, but the general rule is that if you lose money, there's a good reason for it. If you lose your USD from your wallet or your gold from your pocket, will the banks refund it? Why should Bitcoin? Especially considering the price of bitcoin is affected by the knowledge of how many coins there are. Randomly being able to bring those back now, after 4 years of bitcoin mining, would have an adverse effect and probably no one would agree with it imo.
sCrypt
I'd like to hear someone smarter than me explain why we can't have both.