All adjusted to how important the thing you're securing is: one layer of any approach to securing something is generally a bad thing. Making that one layer bespoke doesn't inherently fix that but it does inherently add an enormous burden on you (both cost and time) that could probably have better been spent on another already existing security solution or approach to add in instead.
Is roll your own cyber security maybe a good thing as the bad guys like to work on skeleton keys?
All adjusted to how important the thing you're securing is: one layer of any approach to securing something is generally a bad thing. Making that one layer bespoke doesn't inherently fix that but it does inherently add an enormous burden on you (both cost and time) that could probably have better been spent on another already existing security solution or approach to add in instead.