Personally, I find the padding that the tongue provides important to reduce the pressure from the laces which would otherwise be pressing directly against the tops of my feet for many hours each day during the course of a hike. The tongue also helps to eliminate some debris, sand, etc. from entering the low cut trail runners.
My last pair of boots and my current trail runners are as close to a perfect fit as i've ever had. Yet the roughness of the terrain and its poor footing requires that the laces, particularly on low cut trail runners, be quite tight to keep from losing a shoe as the ankle and foot tries to roll with most steps. I suppose if the terrain/footing is so mild that "flip-flop"/thong sandals are appropriate then loosely tied trail runners would work fine too. ok. I'll admit it - a bit of hyperbole - I'm exaggerating a bit on my last statement - just for the sake of effect.
I would hate to think of the pressure that the laces pressing directly on small surface areas would exert and the localized reduction in surface blood flow in those areas that might result. One or two pairs of think Smartwool liners probably wouldn't do much to alleviate the pressure is my thought (i could be mistaken???). Another round of Decubitus ulcers, anyone? Possibly? As is, with tongue in place, I'm all too glad to loosen the laces at rest stops and sometimes take off the trail runners too for a few minutes.
I'm glad it worked for RayJ. I'm not willing to try this one though. If you try it, i hope it works well for you too.