For Elamite the language we have sources written in the Akkadian script. There are reasons to believe that the few Linear Elam inscriptions discovered today record the same Elamite language. You'd not be writing in a new language, just in a more ancient script of one of the earliest languages where records have been found!

For Linear Elamite pretty much all that is known is inside the new Desset paper and maybe a handful of others. The corpus is less than 100 texts/fragments!