From an adoption viewpoint if you don't have good IDE support that will hurt you. From what I understand IntelliJ has the greatest market share, followed by Eclipse and VSCode. People do use other editors, but they represent a smaller portion of the market and are usually diehard fans of whatever editor they use.
Gradle/Maven will get you building and running, but it alone won't give you syntax highlighting, or auto-completion. That's where IDE and Editor support comes in. You can write your own support/plugins to augment and add on support, however, to do so you have to understand how plugins in whatever IDE/editor you want to support work. Most usually have at least something to help with syntax, but your mileage may vary on that.
"It would be nice not to depend on an IDE to develop the software as well"
Good luck with that.
Leveraging language support will only get you so far, and will limit what's possible with your framework. Although that may be fine and if we're still just talking about adding the trait to the controllers, that might be fixed with documentation. Getting adoption for a framework is hard, you have to offer people something that they can't get anywhere else, and make it easier than staying with what they have always done.
Couple that with the fact that your framework requires Groovy and Grails, so you are going for a niche market to start. Experienced Grails users probably won't use it because they already know Grails and you can get frontend developers to do a frontend. Groovy while an awesome powerhouse language, it is really bad at marketing. People use Groovy to get stuff done, and don't really talk about it. Also, Java is getting "better" with watered-down versions of features Groovy has had for years, so trying to pull Java devs will get harder.
All that said I don't want to diswade or discourage you, just give you an idea of what you are up against.