Not when you want to stick to the Script Developer and the no-programming approach. You can export the test case to Java and apply all the programming magic you like, but you lose the ability to maintain the scripts in Script Developer. https://lab.xceptance.de/releases/xlt/latest/user-manual/03-scriptdeveloper.html#toc-export-to-xlt-scripting-api
If you need some some repetitions, you can use modules and when the count of not determined upfront, you can limit further module calls be setting a variable and use the if expression when calling a module. https://blog.xceptance.com/2016/06/01/conditional-expressions-in-xlt/
We support test data sets by default including CSV. Find more information here: https://lab.xceptance.de/releases/xlt/latest/user-manual/06-datadriven.html
It is compatible and approved by Mozilla for all changes to come including e10s. Mozilla will discontinue the XUL technology by end of the year. We will provide a feature-equal replacement by that time that is fully compatible with all scripts you might have created.
No, Script Developer is meant to be a Selenium IDE replacement to address the insufficient feature set of the Selenium IDE. We provide modules, variables, parameters, test documentation, test data sets, and much more. https://lab.xceptance.de/releases/xlt/latest/user-manual/03-scriptdeveloper.html