I don't know much about Haltec, but here is what I know.
I think that having to keep your stock ECU is a + and not a -, therefore being standalone is not a +.
You don't need to relocate the stock ECU anywhere if you get TEC.
Using stock sensors is a -, as stock crank angle sensor doesn't have enough resolution. Plus, there are only few sensors. MAP, O2, Coolant, Crank Trigger and air temp.