He's got an ISO crank. The question would be why he doesn't just find an acceptable JIS crankset instead, for the JIS taper on the VO BB. That's the way I'd go. And an old JIS crank is likely even cheaper than the aforementioned chorus... OP, what's special about the crank you intend to use?

OP, chainline can be manipulated several ways. For example, if the BB is asymmetrical (IE, the spindle extends out further on the drive than the non-drive side) you can flip the BB around to move the line in. You can do this with a French thread BB such as the VO because the threads are the same on both sides. Or you can re-dish the rear wheel, which also involves moving spacers on the rear hub so the hub is no longer centered in the drops. Or you can move the remaining ring over on your cranks; this can only be done if you've converted a double to a single (Via use of shorter chainring bolts).

When you get into these projects, esp. with older Frenchies, you sometimes have to deal a bit imaginatively with problems as they crop up.

edit: and whatever you do, don't file the crank insert. Sounds like a bad idea on several levels. Really, without seeing the set up in question, it's hard for even a skilled mechanic to make an sort of determination. One of the more irritating parts of the fixie revolution is folks asking over the internet for the spindle length to get a perfect chainline. I recall one fellow who wanted the perfect chainline on an old PX10. He came back and reported he'd found the perfect spindle for the SL crank as a fixie, and now had a perfect chainline, but the non-drive side arm was now hitting the stay (he'd ignored advice telling him he need a longer spindle, and insisted a 103 or some such would give his bike street track cred, or somesuch). You really need to be on the scene, observing, to offer much usefull advice-- as Miami Jim said, too many variables. So you may have to use more than one of the above solutions, or even one that ain't mentioned-- but not the filing, no no no.