You can start by sending your inputs to EMEA-Channel-Support-Configurator@juniper.net - they should be able to pass the request to the right people.
Secondly; I'm a part of the technical advisory board on this tool and will raise the requests as well at our next meeting - but no promises that it can be changed as I see some validations being done at each step. But overall I agree - it takes too long if you try to add multiple types of transceivers.