In general, if I don't use something, if it's outside of my focus, that shouldn't harm security. As an example, given your two secure systems which can combine

In general, if I don't use something, if it's outside of my focus, that shouldn't harm security. As an example, given your two secure systems which can combine into an insecure system, if I don't use that second system I should be good. If I do, I better know their interactions. This argues for a small reliable toolset rather than having every contrivance in the HomeDepot center aisle on my belt. Not full stack, definitely not fool stack, just stack.