For those languages that Studio supports and for which there are spellcheckers but which aren't yet in Studio by default, they should be bundles. It's not really translator-friendly to have to mess with the spellcheckmanager_config.xml file etc. I'm thinking particularly of gd-GB but there are probably others.

Either bundling them or some much more user-friendly loading mechanism where a translator just has to point Studio at the .zip or .dic/.aff files on a local drive and Studio adding them to the spellcheckmanager_config.xml itself and putting them in the right directory.