Waaahhh.... how can an awesome software like git have such an awful extension like submodule? I think I might go writing my own implementation, dealing with the problems of submodule is too time consuming!
I could not hold it anymore and wrote git subgit (useable as yadm subgit, too) which is much easier to use as submodules with 81+ different git projects cloned. It needs a bit more testing and a license.... I will release in a few days.