The Gateway never really made sense when the radiation environment makes any long duration missions impractical without a massive cosmic ray water shield. Eugene Parker explained this for the layman back in 2006 in a classic popular science article published in Scientific American: Shielding Space Travelers.
In combination with dosing is micro-gravity debilitation which also causes permanent damage and there can be no real progress in Human Space Flight until this issue is settled. Especially for young females, a near-sea-level-radiation one gravity environment is the prerequisite for multi-year missions. There is no way around it.
Dosing and debilitation is best addressed by way of three techniques. The first is a massive water shield, as detailed by Eugene Parker, and the obvious structure to contain this shield is a wet workshop, and better yet, a double envelope “Fat Workshop.” It follows that a tether system several thousand feet long to provide artificial gravity would use these workshops- which are already built to withstand max-Q launch forces. The third technique is to bring the water shielding up from the Moon using robot Landers. Bringing these thousands of tons of water up from the Moon requires 22 times less energy than bringing it up from Earth.
The Fat Workshop is going to need a Super Heavy Lift Vehicle in the 130 ton payload (or larger) range.
Ice on the Moon 