Would it be possible to group the available MT engines in a fixed order, that's always remembered?
(For me this would be: Google Translate / Microsoft Translator / Yandex)
The Matchboard is the place for grouping resources.
I can see that you want to promote the Matchboard, but perhaps you can facilitate users that don't want to walk that path? After all, that's what's make CafeTran anarchic and extremely useful.