Nope, I meant what I wrote.
You don't need an MMU, because you have no need for virtual memory or similar.
Checking an integer is within some bounds is a much simpler problem, and in some cases the check can be elided through analysis on the code.
unfortunately, then, you'll need new CPUs. You don't _need_ memory protection but CPUs today are built on the assumption that you are using it and have thus stapled many critical attributes about memory to it (such as cacheability and shareability).