Technically the main problems could be overcome... that is the transpired moisture issues (think about grow op houses that are destroyed by the water in the air, the floor being able to take the moisture and still not hold it in too well, it has to drain as well.. Plust it will be much heavier per sqft than normal floors so that must be accounted for in the structure. I have maintained ponds and water lilies in my house along with other growing options without water issues or mold.
But the biggest issue I see is plants that can actually handle that level of traffic, with the very limited light we have in our houses. Even brightly lit houses are often many times less bright than the outdoors. And even under ideal conditions the toughest of traffic tolerant plants don't take that much traffic. I hate mowing grass so I have studied many varieties of ground covers and very few are anywhere near as tough as grass, and even fewer will tolerate low light and variable moisture conditions. Even worse the traffic resistance decreases as the conditions decline. So as the light gets dimmer, or the moisture and fertilizer declines from ideal so does the tolerance to traffic (at leas tin any plant you'd actually want to walk on. Lawns and such work because the level of traffic is very low relatively speaking. Floors see very heavy traffic.
The level of lighting you are talking about needing is not easy to provide. not without considerable expense. You can put in windows and skylights, but they don't work when its dark out, and in the winter, its dark more than its not.Skylights, windows , all are expensive and offer limited insulation values. even the very best are about 1/8 as efficient as a typical wall. and much less as compared to a ceiling/attic. Artificial lighting at that leve4l is expensive. 1000W metal halide vapor lamps will do about an 8'x8 area at something just under solar lighting levels. These are expensive lights and draw a lot of power... more than the 1000W on the bulb.
Overall I can't see it would be worthwhile or cost effective and certainly not "ecologically sustainable" ...
