I understand where you are coming from. The total water needed is the total water needed and it does not matter how much is below the false bottom as long as it is drained in the end. While I do mostly BIAB brewing, I do have a mash tun with a false bottom. My dead space is .5 liters and I have approximately 1.25 liters below the screen which is always recovered. For an average gravity batch of 20 liters at 1.050 gravity, I need approximately 31 total liters of water (0.5 liters to dead space, 3 liters to grain absorption, 6.5 liters to boil off, 1 liters left in kettle, 20 liters in carboy). This does not change if I do not have the water between the bottom of the screen and dead space. I still have the same total water demand.
In my profile, I split the water for mash and sparge to get approximately equal runnings from both, centered around a typical recipe. Thus my strike water is 0.5 liters for the dead space, 3 liters for grain absorption plus half of the remaining water (13.75 liters). For a 6 kg grain bill this gives me a mash in at 2.875 liters/kg of grain (1.4 qts/lb). If I omit the recovered water, my actual water in contact with the grain to grain ratio 2.8 liters per kg or 1.34 qts/lb. Because this is centered on the majority of my brews, the actual ratio of water in contact with the grain will vary slightly, but will always be consistent.
As the grain bill increases, the actual water to grain ratio will increase slightly, which helps to maintain my efficiency fairly consistent. As the grain bill drops, the water to grain ratio will drop slightly to 1.25 qts/lb of grain, still in a comfortable place.
Personally, I don't see this as a limitation, but rather a constant which is easily managed with the mash profile.