>With IPv4 the router will just fix up NAT. With IPv6 you now have to deal with significantly more complexity.
How so?
In a multihomed environment, you'd still be PAT'ing to unique addresses on the WAN side (unless a FHRP is in use, which would be rare) - if one of those links go down, so too does all of the flows associated with address of the link. If no dynamic routing protocol or redirects are in use, the gateway with the down link will also eat half (assuming two gateways) of all egress traffic.
IPv6 should be easier as no NAT/PAT is in use, therefore you have no challenges with statefulness or routing symmetry.
It SHOULD be easier. It's not on current widely available prosumer hardware.
Yes, your connections will get temporary eaten. But for the typical developers workload that won't be a huge issue because most connections you do are short-lived. Configuring all your clients to properly switch vs. configuring your NAT router (with builtin functionality for exactly that) is orders of magnitude more complex.
With IPv4 the router will just fix up NAT. With IPv6 you now have to deal with significantly more complexity.