I'm wondering wether it is possible to make a loaf (not brick) with 100% wholemeal flour?
Maybe using vital wheat gluten in the 100% wholemeal poolish starter? if so.... how much would be used?
Several recommendations for avoiding bricks and making good 100% wholemeal:
Using old dough [pate fermentee], as your pre-ferment, works well. Pre-fermented flour anything from 10 to 30% depending on your taste in bread.
Definitely use an autolyse of 1 hour minimum, up to 4 hours, of just the flour and water in the final dough.
Hydration is where most people go wrong. Hydration for good quality strong flour should easily reach 72%, but the autolyse is essential as it gives plenty time for the bran, germ etc to break down and take up as much water as the flour wants..overall.
Additionally, if you haven't read Peter Reinhart's work "Wholegrain Breads", I strongly recommend you do. This will give you an understanding of the enzymatic reactions as well as the fermentation systems used.
You don't need any additives, not even any fat, but you do need to know how to create the best dough quality possible and a good fermentation system. If you have these and maintain good temperature control you're there.
Maybe a little warning: overly long ferment are often avoided with 100% wholemeal, as the high ash content tends to lead to rapid fermentation and can mean the dough breaks down fairly quickly; hence why I recommend you try pate fermentee rather than unsalted sponges.