Hello, I'm back with my research into the matter. Usage of .unsafeFlags is discussed in Confused by unsafe flags being disallowed in dependencies and in this thread is a mention about PR "removing restriction on .unsafeFlags on local and branch dependencies".
Contrary to my previous post, I'm not going to open a new topic on the Forum since such topic already exists. I still don't feel like I understand completely all the implications of using .unsafeFlags and I think that the documentation should explain this feature better.
That said, I'm not going to start the duscussion now, as my time has run out for today 
I will keep my eye on the issue and maybe looking into this in near future.