I've done several wall quilts with big stitch. I used #8 perle cotton and a size 8 quilting needle.
My problem was starting and ending invisibly. If someone has figured that out I'd love to hear about it.
Re: dangerous for little toes and fingers, these aren't toe catcher stitched, they nestle into the fabric, you'd need to use something to pull them up. It really is a lovely quilting option.
Re: embroidery floss, absolutely you can use it. If I remember correctly the Japanese white on blue version was done this way. It began long ago to keep layers of the jacket held together for warmth and longevity. But we always find a way to make sensible to include beauty also, don't we?