A Boring Dystopia

This would be terrible business if any pharma worked this way. The vast majority of potential treatments fail either in the lab or in early phase trials. It is not very likely that'd you'd be able to on-demand develop a novel treatment for symptoms before one of your competitors figured out your already-discovered cure. That would be unless you patented the cure, but by the time you spent years developing a new symptom-only treatment and testing it through each phase, you'd have a few years at best before your exclusivity on the cure patent expires and thus your treatment becomes worthless.

Pharmas are run by the same short-sighted wall streeters as every other corporation. Actually successfully executing this sort of long-term plan would require thinking further ahead than a few quarters, which they are not capable of doing. A new cure is a big stock boost now that they could never resist.