In other words, there's probably a market for a model trained on a curated collection of high-quality code.

That is what we have today - it's why Opus 4.5+ and GPT-5.2+ are so much better at driving coding agents than previous models were.

Doubt it”s sustainable. These big models keep improving at a fast pace and any progress like this made in a niche would likely get caught up to very quickly.