One of my main concerns is when the firewall stops working (due a poisoned packet what shutting it down, what would be the first logic kind of attack I guess) currently the access to the "local" network would be granted with IPv6; the network becomes the same as the attacker's one.
I put the CVE links with the generic word "firewall" because it is the point where the "local" vs "internet" resides with blind faith within IPv6 (without indicating an specific exploit, just vulnerabilities exist). For this case, the DDOS and buffer overflows that force the firewall to shut down, or code execution, what are periodically discovered, is what I wanted to show for being considered as a serious problem. Not everyone reports firewall bugs, and others I guess even wickedly insert them.
With NAT setups, the local and internet networks are different between them, what requires the packets to be filtered and rewritten by NAT for the address what solicited it, while unsolicited packages are discarded. The NAT in consumer gear is run mainly by software, but a poisoned packet will not aim to shut it down for network penetration because it would be the end. If the NAT stops working, the doors close for everyone.
It is about the double checking,
-IPv6 without NAT: If the firewall stop working, opened doors. Feast.
-IPv6 with NAT: If the firewall stop working, many rules get unfiltered, wild. But NAT keeps the local/internet separation besides filtering unsolicited packages. Not absolutely secure, nevertheless keeps being a complex target.
Like all of we, I suffered some problems that NAT can bring losing countless hours trying to make work some specific services, but when I first read IPv6 didn't implemented NAT nor something similar in the protocol (for whom whish to use it at least...) and what the supposed local IPs are merely part of internet (link-local addresses that aren't routable as first target, devices with internet connection are), each device with its own public address, I doubted seriously about what was going on.
Given that even Mikrotik RouterOs periodically have security vulnerabilities related with the firewall, I can't conceive the idea of people relying on firewalls rules to do the home/internet separation within IPv6 (plus the public address of each device gives me also anxiety), as it is a matter of time before such separation ceases to exist; it is like the crossing of fingers.
I mean, it is not a matter of misfit, it is more like the users will not even notice the router's firewall was shut down.