Bang for buck ML system?

[SkvLTD]

So I have a debate on my hands - attend the Firefly Music Festival (free) for which I will need to get me a ML + some pancake to pass it off as non-removable lens/pro camera not be bored stiff for 3-4 days, or to sell the tickets and not put off some work that weekend.

I'm Nikon FF invested, but our ML offerings are pretty bleak for low-light and almost any performance save the AW1, because that + some sort of underwater wireless flash rig may be WAY cheaper than messing with housings that cost 4x more and an interesting venture for the summer.

So what would you guys recommend? Budget would preferably be as low as possible and not quite A7 high since I won't be using this setup aside from festival environment which I don't know how often will be for me aside from this one. Don't need a whole other FF rig with no glass, flashes, etc. Then there are these metabones adapters that effectively push crop performance up to FF, right?

[jamaeolus]

[SkvLTD]