Where to put the commission dollars?

My thoughts are that you're basically paying for 2 different things with both scenarios. For scenario A, you're paying for time - its going to take time to do all the rank and file, but they're not particularly detailed or difficult; for scenario B, you're paying for skill - to make sure your characters/centerpieces stand out and look fabulous.

If you think you can do justice to the characters if given the time, then scenario A makes the most sense. Typically with rank and file you don't need them to be exquisite - they're going to die in droves, or be in transports and not on the board, and so don't really warrant the high price of top quality commission painting. Instead, get them done to gaming quality - a base, wash, highlight, and nice base. They will all blend together on the tabletop regardless, and as long as they're done and taken off your plate, you can focus on the characters and really make them your own.

If you don't think you can do the characters justice, but have the time to churn through basic base+wash+highlights on ~200 models, pay the higher price for top notch work on the characters. They'll stand out, look absolutely stunning, and since they'll live a lot longer than your rank and file people will see them more often and up closer than nameless guardsmen who die as their chimera explodes.

Either way, you're probably looking for $3-5 per model for the rank and file to be done to a table top standard (though some painters do bulk pricing and discounts on whole armies), and about $25-40 per character at top-level quality if I'd have to bet. So its a matter of what you want more - time back in your paint schedule, or seriously beautiful characters, or both if you've got the coin for it.