Advise needed on creating a Java Systems Integration Testing Framework

I got a 10 year old SIT Testing framework of my application.Its beautiful and I love using it and adding new test cases as we progress.I joined this project only recently.It is a XML based framework where we formulate test cases and call a java program.The java program uses DOM, parses the XML tags and invokes my application code with the inputs we configure in the XML. And the output once received is asserted,converted to XML and written to a output file. All is good.

So I got 5,10,15,20.... tests in 1 XMl file and have close to 120 XML files which covers around 85-90% of the code

Now - They want to explore alternatives. Not for any specific reason but because they have been using it for 10 years. They wanted to know if anything is out there in the market which will improve things. I got to recommend alternatives to them if any is better than the current framework. Even if its going to cost not a problem.

I researched a little bit and see here that google spock is an option

Please advise me on this experts

Integration testing tests the system extensively by mocking any input data objects etc etc. And we heavily do regression too.

We prefer to use Java