Mitchell,
It would be straightforward to formulate a similar theory  including gravity, electroweakish gauge fields, and real fermion fields  using only F4 instead of E8.
A modified BF formulation of YangMills is equivalent to YangMills, just vary the action with respect to B and plug that expression back in. The advantage of a modified BF formulation is that it naturally gives the Dirac action for fermions, via the pure BF term for that part of the algebra. It should be very interesting to calculate how these parameters run, and how the formulation connects with approaches to quantum gravity.
kneemo,
Thanks for pointing out the reference.
