1) the northstar system has more parts availability, and is still fairly compact. not much more.
2) should be no problem for the arduino to do minimalist data distribution for the 8 coils.

The coils we will probably use are the LS engine coils (4.8L, 5.3L, 6.0L, 6.2L). They are fairly small, and mount on the valve covers with short plug wires to the spark plugs.
There are aftermarket coil mounting kits from EFI connection, and some others.

I hope I will be able to make a prototype this winter, but my toddler might be busy distracting me. 3yr olds....all energy, no focus.