How to build a JrElastic multilingual-based site using the Site Builder?
Using Jamroom
The things you are looking to do are difficult to do with Site Builder, it would be easier no to use it in this case.
The $_user variable will contain the language that the user has chosen which can be used in templates, but there is no site builder button for it.
Same thing for the sections. It would be easier to use an {if} template block than to try to do it with site builder.
Jamroom was previously developer focused. Site Builder has come along as a response for the need to have a system for non-developers. You can still do more by editing the skin templates than you can with Site Builder. Your suggestions are good ones though and hopefully with time we can get those systems integrated.