It seems you want Mobile.asyncWaitForElementPresent which works asynchronously. You want to register a Groovy Closure as a callback, and timeout. As you know, all of KS built-in keywords are synchronous. There is no async type of keyword. That is something completely new. I have no idea if its feasible in KS or not.
I suppose that Image comparison is an alternative approach to check if anything UNEXPECTED happened. You want to take screenshots twice: before “normal test case” and after “normal test case”. And then create “diff” between the 2 images, with which you would find unexpected things if any.