Engine Movement bonuses

[Demorve]

I'm looking for some idea's on how to add extra bonus movement points to engines once they reach level 6. As it stands now to me once the engines reach level five it becomes wasteful to research levels 6 - 10 merely to gain extra supply storage. I'm looking to add one mvement bonus at level 6, two at level 8 and 3 at level 10. I believe that by adding these movement bonuses it makes the lower level engines more attractive. You now would have to make a choice between a sixth level Ion Engine with a bonus movement of 1 and more supplies or do you move on to the Contra - Terrene Engine. I would apply this formula to all the engines so that when you reached level 10 Quantum Engine a frigate would have a movement total of 18.