To me this sounds like a bad misunderstanding of regression and your use case. If you need a system capable of predicting within an interval, you should use something different, for example you could use Bayesian regression with a prior that only has support on your permitted domain.

You very much should be choosing models that actually map to the physical reality of your problem domain, and not using something that is fundamentally unphysical for your use case, but attempting to correct it with hand made business logic.