As I said, floats can provide results that are no worse than a specified fixed point type. So if you want uniform absolute precision, just round down to the required precision.

Floating point is generally deterministic in practice with a fairly minor amount of effort, the major remaining issue being library rounding. I actually wrote a library that guarantees this for arbitrary code, with some small, obvious caveats like standard library precision. And the conference talks linked above note, the standard library issues are an increasingly solved problem for modern toolchains. The remaining cases are mostly things you won't do in fixed point. Let me know if you're aware of anyone computing erfc in fixed point for determinism though.

I'm not saying there aren't any situations where other systems are justified, but you probably won't know if you fall into any of them without the kind of numerical analysis that most codebases will never receive.