I don’t want to break your enthusiasm, but with Maven and Gradle, I think the most powerful/best possible build tools already exist… When you craft a completely new project, the problem is that you will never have enough manpower and knowledge to compete with eiter Maven or Gradle. Instead, try to intensify you experience with Maven and Gradle and try to figure out what you like about them, or where you see room for extension and enhancementss - don’t ask others, ask yourself first.
I think there are very few things that are truly horrible with Maven, everything else works pretty good or perfectly. What totally kills me is the testing utilities Maven offers - everybody knows how important it is to provide simple and easy-to-use tools to test your custom Maven plugins. Sadly, integration tests are barly possible, because the documentation for the testing-harness stuff is so long outdated, the examples don’t work, version conflicts exists etc. So why don’t you implement the functionality you need with Maven (or Gradle) - and first take a look at how far you could get? Since you’re using Ant for your build project, I assume you’re not too familiar with Maven and Gradle. But this should be your first go, I think.
As I said, I don’t want to break your motivation - but especially Gradle is very very generic, you can literally do anything you want, while Maven is just a bit more restrictive.