Converting BNW will take longer than a couple weeks I'm sure.

I expect you could be quite helpful even with a couple week break. Those playthrough reports on AI happiness alone were quite valuable.
Play testing what they changed will probably take about that long even before making simple modifications. I agree with Mitsho, and in previous debates with others, that things like the VEM/GEM policy trees, the value and effects of many buildings, the unit combat balance toward strategic "elites" and the vanguard tree, or the diversity of added/changed wonders, many leaders changes, and so on will be easy things that we will want to see modified again regardless. Those are the bread and butter of the VEM/GEM project is enhancing things within the vanilla game in not just a "MOAR!" way but to make them interesting decisions rather than brain dead or boring as vanilla often has. What should be built here should be an interesting question, that sometimes has an obvious local answer, and sometimes depends on overall strategy or capabilities. That kind of thing. If we can ignore things from our decisions because they're very rarely useful, that's less interesting.
The trick here is the balance of the AI's general performance and the economic balance (units versus infrastructure versus income), along with other things like the value of coastal cities and naval units generally. That will take time to balance and re-balance, and may be seasoned to taste. As it were. And BNW looks to be making a number of dramatic to modest changes on this front already that we will need to look into.
I'm not sure, but it almost seems like a lot of the lua may as well be written from scratch at this point. Some functions, like the Machu Picchu mountain event, could be copied back in and made to work again but a lot is UI functions that seem to have hit some bugs either from patch changes or just have become generally unstable from version to version (the gold income bug, or the AI's faith accumulation). I don't know if it would be better to reinvent the wheel here or to gut it where it no longer works or is unnecessary. Github might be the best way to approach that so that Thal and other programmers can collaborate on removing extraneous bits and documenting code somewhat while creating a unified project.