It sounds like what you're describing is one-time allocation, and I think it's a good idea. There is some work on making practical allocators that work this way [1]. For long-running programs, the allocator will run out of virtual address space and then you need something to resolve that -- either you do some form of garbage collection or you compromise on safety and just start reusing memory. This also doesn't address spatial safety.

[1]: https://www.usenix.org/system/files/sec21summer_wickman.pdf