Container pot mold is not a issue, ALL of my autopots have it on the top soil and when i used fabric pots without autopots i would get mold on the bottoms of the pots, never was a issue, i'm told its healthy
As for stagnant water, how does that happen in fabric pots? if they are lifted up off the ground or sitting on clayballs (hydroton) this won't happen, its REALLY hard to overwater in those pots