That is an ambitious project. The problem is that the ECU controls the engine and it won't let it rev up unless it thinks it's in Forward. It also won't start unless it thinks it's in Neutral.
You have a few options as I see it. You could get the ECU of an 08 where there is no iBR and then if you keep all those electronics it should work. The other option is to hook up the iBR unit(anywhere in boat) so it thinks it is going from N to F. You'll also need to have the handle switch(or suitable switch) to change from N to F. Another option is to have the ECU remapped to remove the iBR function completely. I believe RIVA does this.
You are also going to need to keep the gauges as they are an integral part of the system.
Would like to see some pics.
