This counters the argument that Meridiani could not have been a long lasting lacustrine or oceanic environment because of the lack of a basin there.

No it doesn't. Again you're posting stuff without reading it, or thinking what the words actually mean.

Sure, there is an underlying basement trend which is basin-like and may well be a very old impact basin.

But NO there is not a large modern-day closed topographic basin, nor was there when the Meridiani rocks were deposited. The whole area is tilted on a slope. The business with associated channels and basins is a second-order focussing not a first-order closed topographic feature.

Figures 3 and 4 make this quite clear.

There may well have been groundwater drainage through the area - that's the essence of my Sabkha model, anyway, but there was not a regionally-defined closed topographic basin within which one could form a lake on the scale required for the Meridiani deposits.

Further, we already know that the Sulphate deposits have a significant H2O content as water-of-crystallisation and this is stable even in Mars' atmosphere, so the epithermal neutron counts are responding to this crystalline trapped H2O, not to "water" per se. (nor ice, nor steam, nor strawberry gelati)