Recently I have been compiling a lexicon for a vocabularly learning program, I am hoping to record about 500 words of Latin for this project, and so I have been brushing up on a great deal of Latin words for contemporary objects.
Of course, even relatively recent NL dictionaries fail. I haven't found anything for "video game controller" yet. But in the course of this I have been musing on one of the problems of Neo-Latin: the fact that it is almost always circumlocutions.
For instance, I discovered instrumentum portabile radiotelephonicum for 'cell phone'. Now, this is not bad Latin. It's just that I can't imagine Neo-Latin speakers getting out such a mouthful in everyday conversation. Sure, we can talk about semantic density and what-not for a while but at the end of the day, just as we don't say "cellular telephone", why on earth should we settle for instrumentum portabile radiotelephonicum? I suspect if we have a genuine Latin-speaking community, not just (some very, very) enthusiasts, we'd just have 'portabile'.
Neo-Latin is in a relatively stronger position than the difficulties encountered by those interested in using communicative practices for teaching Koine or Attic Greek. What do you do for objects and concepts that just don't exist in the language? Do you create Koine neologisms for 'video game controller'?
Personally my preference for Greek is to retro-engineer Greek terms from Modern Greek. Find the MG equivalent, then 're-classicise' it: work out an appropriate CG or KG form, place an appropriate accent, and decline as usual.
This last month I've been reviving my interest in using Duolingo, and we all dream of the day the Incubator gets opened up for English -> X languages, so as I advance my German, I've been taking notes and preparing a lexicon so that a Latin and a Koine Greek course might get off the ground post-haste. It also does a lot of good to be refreshing my own conversational skills in these ancient languages.