The argument for actual intent is based on how it was sold to voters when the laws were first enacted. I think it's perfectly legit to judge patents on these terms.
Tort law, for example, predates the U.S., but today we have an economic understanding of what purpose it serves (addressing the negative externalities of risk-creating activities). It's perfectly legitimate to look at those modern economic models to decide how we interpret (and evolve) these existing laws. With regards to patents, we can understand them as a solution to free-rider problems. Regardless of what intuitive understandings motivated them in the first place, the laws should be interpreted with the economic model in mind today.