It uses the GC from the JS engine for it's entire DOM implementation which definitely makes it tricky. There are also some other bits you'd probably want to rip out like gstreamer for media support.
We looked at using Servo's layout support. But it isn't really designed to be used standalone (although it could be if that was prioritized!). And we'll probably add a Webrender rendering backend at some point (Blitz is designed to have pluggable renderers).
