The 3.7 litre upgrade route has been extensively tested by Hartech, it's a development of their existing rebuild - the difference being 100mm diameter liners instead of the 96mm stock, and new pistons. They keep everything else the same as the rebuild, but that includes closing the deck as part of the rebuild due to the new liners.
What we're adding to that proven recipe is new cams, possibly some head work (although from stock the heads seem to flow exceptionally well) maybe a compression bump.
Port velocities on the stock head at stock capacity are actually very low for a modern engine - the increase in capacity both unshrouds the valves and increases pumping efficiency which brings the port velocities much closer to what we'd expect to see - but the cams are, as previously stated, a compromise for the 3.4, let alone the 3.7.
I don't think we're doing much that is totally new, hopefully what we're doing is, via testing and calculation, adding to and refining an existing recipe.
Fitting a Mezger might be cheaper, it is true - but I enjoy the project, the research, design, finding the parts etc. Also, it's fun to make the (very much unloved) M96 into the engine it might have been - an extension of the X51 program, if you will.