The first meal I got from BA was some sort of poached Cod with ramps. Ramps I had never heard of although I understand now that some people get very excited by them during their short season. (I think I've seen them once in a grocery store--Whole Foods naturally.) However, I'm pretty sure that if you substituted scallions, the world would not come to an end.
I think you're spot on with that last assessment. Generally those ingredients I mentioned I'm sure don't make a big difference over some other reasonable substitution.
For me, it makes for a nice change of pace anyways and as I've mentioned in another comment the BA meals tend to be quicker/easier to prepare than my normal cooking so that's also a nice change of pace. I tend to order one shipment ever 2 months or so on average I'd guess.
