Well, yes, of course it changes things. Editing in Lightroom means your photos aren't as good as they should be.
However, for this particular issue, no, it doesn't make any difference.
No Brian. PLEASE concentrate on the actual issue.
Mary needs to know how to read the temperature of the ambient light, then match her flash to that temperature.
I figure that she needs a light meter to take the reading, yes?
Then how does she modify the flash temperature? With the gels you mentioned?
Inkjet is fine, as long as you tell it to only print with black ink (and as long as you check closely with a magnifying glass afterwards to make sure it has done so).
You are absolutely right. I figure it would be best to do it at night, with a light shining in towards them from outside, giving them the rim light you want.
Ah, give them a chance, I guess.
Don't change your editing workflow, of course. Just convert your file to Adobe RGB when you're preparing the print file.
Alas, no, it's too clumsy. Much slicker to keep them as two separate actions, and have them set up as two F keys on your keyboard. Eg F2 to run the BW, then choose the layer/s, then F3 to save the PSD.