Yes, one-time-pads are insecure; they have no mechanism for message integrity. However, that’s a side issue.
There’s a reason our files tend to have things like magic bytes at the beginning that tell us what sort of file they are; our lives would be more complicated if these things are missing. Direct cryptanalysis is generally the least of our security worries. Measures like those you propose make things stronger where they are already strong enough at the cost of making them weaker where they are already weak.
Yes, one-time-pads are insecure; they have no mechanism for message integrity. However, that’s a side issue.
There’s a reason our files tend to have things like magic bytes at the beginning that tell us what sort of file they are; our lives would be more complicated if these things are missing. Direct cryptanalysis is generally the least of our security worries. Measures like those you propose make things stronger where they are already strong enough at the cost of making them weaker where they are already weak.