Honestly, I think it'll be kind of a given that Index III's visual assets will be heightened from previous seasons, since that's how it's always been with the series. Index II looked pretty neat when compared to Index I, and Railgun S looked amazing compared to Railgun, so it makes some decent amount of sense that more budget will make Index III look somewhat similar to what Railgun S did. Unless Miki had to scrape the project off the ground so badly it was only approved under tight-ass budget, but I don't think that's likely.
So let's not start wishing Nagai's incompetence at directing things with substance in recent years onto Index III...