In the old backend there's a built-in numeric value validation mechanism that looks like:

syntax:expression: $VAR(@) >= 128 && $VAR(@) <= 16384

Its design is quite odd, for example, one could put this in a template with type: other than u32, which raises a question if u32 type is redundant. It also would be quite hard to extend to support non-integer values.

The mechanism of external validators in the 2.0-style command definitions is more flexible and could easily allow this. We just need to implement a validator.