Serious question: what’s the best title to use for an engineer that will be the contact point for a customer on a big project? Bonus points for something that is easily understood internationally.
I normally avoid titles, but in this case it’s kinda important.
Thoughts from a wondering mind 
Field Application Engineer (FAE) was who I always dealt with at an ISV.
“Technical” rather than “Engineering” suggests you are not necessarily an engineer yourself, which may be useful, depending.
Here are some thoughts: Engineering advisor. Technical consultant. Engineering liaison.Technical Solutions consultant/manager. Client services engineer.
when you say international, what languages or countries?