If english is not lingua franca...

I think I read somewhere that Esperanto, a custom created language of sorts, would have been a good candidate for a global language due to the relative ease of structure concerning possessives, gender, sentence syntax, etc. Imho, it's pretty unpopular though, and I too would prefer something more well-known to have a possibility of spreading such as Latin. Might as well put that dead tongue to use if people are still being made to study it!

Jam it back in, in the dark.

Having never taken Latin, I wouldn't know for sure, but I recall that Latin has free word order in terms of where subject, verb, object and whatever are placed, as long as you conjugate something in a particular way? I already found that confusing in itself, especially being already used to the syntax of English where word order is important.

In addition, I think a major language that doesn't have a complex syllabary or radically different alphabet would be a good candidate. Not like Japanese or Chinese, but moreso French, German, or Spanish. Then again, that's biased considering how I'm already accustomed to English and learning a new system would seem foreign. The point of view could easily be switched around to, say, a Russian Speaker.

I think that this also brings up the point of written vs. spoken.

There's nowhere I can't reach.