Would it be possible to create a program with which to create a cryptographic algorithm (i.e. encryption or hash) using well-known elements of other algorithms in the same way that algorithms "reuse" systems such as Feistel's structure? That is, eventually decide to use an algorithm that combines the Rijndael KeySchedule, and the Pseudo-Hadamard Transform. All this correctly applying the concepts of diffusion and confusion of Shannon.
The objective of this would be during a communication to change cryptosystem repeatedly, so that if you want to do cryptanalysis of the messages you have to do cryptanalysis on several different algorithms. In this way a kind of PFS (Perfect Forward Secrecy) would also be obtained.
EDIT: I wasn't proposing the use of security by obscurity, in fact I thought the negotiation of the new cryptosystem as public, in the same way the negotiation of the cryptosystem in TLS is public, and only the key is confidential (being shared using a well-known key distribution algorithm, like DH or RSA). On the other hand I know the definition of Forward Secrecy, that's why I said "a kind of". I was referring to the scenario in which an attacker discovers a vulnerability in a previous algorithm, but because currently is being used another totally different, the cryptanalysis is different now, and the information transmitted before and after the broken algorithm would remain unrevealed, similar to the concept of PFS.
Regarding the use of algorithms already used (and therefore proven in theory their safety), I do not plan to create a new system that is adopted worldwide (or even on a small scale), I only played with the possibility of creating a system like this so that, for example, the AES is found to be ineffective, not all communications made since the adoption of the AES (or any other algorithm) are disclosed. I mean, I propose the possibility of not trusting a single algorithm, and given the problem of the existence of infinity of communications, the solution would be to generate infinity of algorithms.