Why? Because I can. So I did and wrote a howto.
http://blog.one-it.de/ipv6-via-sixxs-using-mikrotik-and-openwrt/
Introduction
As discussed in the previous article in this series, the only real possibility to build an affordable home laboratory is MikroTik. One of the coming challenges in IP is IPv6, and the easiest way to get this is SIXXS.
There are three ways to connect to SIXXS and bring global IPv6 to our test lab – 6to4 static, 6to4 heartbeat and AYIYA. 6to4 heartbeat and AYIYA need a special client (aiccu) that is not supported in RouterOS and 6to4 static needs a static endpoint, which we usually do not have as DSL customer.
Luckily, RouterOS has a virtualization feature named MetaRouter and there is an OpenWRT distribution that is patched for MetaRouter. So the plan is to use this with an OpenWRT MetaRouter to establish SIXXS connectivity.