Suggested improvement for Naval Invasions: when you stack fleets together, you should be able to straddle corps across them. For example, if you have an infantry corps with 10 infantry in it, then you would require a heavy fleet with 10 ships in it. Even if you stack all your heavy fleets together, you are still required to have a single fleet capable of shipping the entire corps together. Therefore, two fleets, one with 8 ships, and one with two ships, stacked, would be able to carry the entire corps to it's destination.
I appreciate the programming for this next suggestion might be more complex, however, you should be ble to stack a heavy feet with a light fleet and achieve the same effect.