> suggest how to do it only for outbound tcp6 handshakes too.

Here you go:

    ip6tables -A OUTPUT -t mangle -m multiport -o eth0 --protocol tcp \
              --tcp-flags ALL SYN --dports 80,8080,443 -j MARK --set-mark 6

    tc qdisc del dev eth0 root
    tc qdisc add dev eth0 root handle 1: htb default 1
    tc class add dev eth0 parent 1: classid 1:6 htb rate 10000Mbps
    tc qdisc add dev eth0 parent 1:6 handle 6: netem delay 100ms
    tc filter add dev eth0 protocol ipv6 prio 1 handle 6 fw flowid 1:6

Although, I would personally throw in an extra class to add 200ms delay to legacy IP protocol:

    iptables -A OUTPUT -t mangle -o eth0 -j MARK --set-mark 4
    ip6tables -A OUTPUT -t mangle -o eth0 -m multiport --protocol tcp \
              --tcp-flags ALL SYN --dports 80,8080,443 -j MARK --set-mark 6

    tc qdisc del dev eth0 root
    tc qdisc add dev eth0 root handle 1: htb default 1
    tc class add dev eth0 parent 1: classid 1:4 htb rate 10000Mbps
    tc class add dev eth0 parent 1: classid 1:6 htb rate 10000Mbps
    tc qdisc add dev eth0 parent 1:4 handle 4: netem delay 200ms
    tc qdisc add dev eth0 parent 1:6 handle 6: netem delay 100ms
    tc filter add dev eth0 protocol ip prio 4 handle 4 fw flowid 1:4
    tc filter add dev eth0 protocol ipv6 prio 6 handle 6 fw flowid 1:6

...just to be compliant with draft-howard-sunset4-v4historic-00 once it becomes RFC.