This part was less funny, I didn't expected it would be so complicated to create a good lowres for normal map baking.
But after tons of try and error, I finally get my workflow ready (well I hope).

MoI is really great for this kind of game modeling. Something really cool is to able to export a very draft version from MoI.
The mesh was really usefull to see where place vertices to get the best curve approximation when buidling the low res cage in Modo.