Ability to change virtualized NIC type with KVM compose for virsh driver

Hey MAAS folks, I was testing out the KVM compose feature which is working great, but for some reason in my environment I cannot get iPXE to boot with the default virtio virtual NIC (it never completes initialising devices). As a workaround, both the e1000 and the rtl8139 virtual NIC models work just fine if I change the definition.

It would therefore be handy to be able to change the default virtual NIC or even the domain template for the virsh driver.