It is an adverb that means “would be better“.
It is used as "v1/n1/adj1+ (なら/は)まだしも、+ v2/n2/adj2". It is used when comparing different options and saying that choosing one(v1/n1/ adj1) is acceptable/better, while the other one(v2/n2/adj2) is not preferred.
Ken and Leo are reviewing documents that their subordinate created.
- Ken: Take a look at page 3, 5, 9, 11 and 15. It seems that there are errors in the numbers and the comments for them should be revised.
3,5,9,11,と15ページを見て。数字が間違っているし、そのコメントを修正しないといけないと思う。 - Leo: Indeed. (Sighs)How long do you think it will take for him to fix them?
確かに。修正するのに、どれくらい時間がかかると思う？ - Ken: Hmm, it will take more than an hour. One or two of them would be fine, but any more than that will overwhelm him.
んー、一時間以上かかるでしょう。一つや二つならまだしも、それ以上は大変だね。
Meg is dreaming about working abroad.
- Meg: What if I could speak English fluently. I’d like to transfer to the New York branch.
流暢に英語を話せたらなぁ。ニューヨーク支社に異動したいな。 - Amy: I think that your English is excellent. You’d be able to work there if you applied for the transfer.
英語、上手いじゃん。異動を申請したら、向こうで働けると思うよ。 - Meg: My level of English proficiency helps me survive while traveling, but working abroad is out of the question.
旅行はまだしも、海外で働くの無理だよ。
Ken was late for work and left some important documents for the meeting.
- Leo: There are 30 minutes left before the meeting. Do you want me to print out the documents that you created?
会議(が始まる)まで30分だね。資料を印刷しようか？ - Ken: Thanks. Let me see…(he is looking for them) OMG! Although I was preparing those documents all night, it seems like I didn’t bring them here.
ありがとう。どこだっけ...しまった！徹夜して資料を準備したのに、家に忘れてきた。 - Leo: It would be alright if you were just late, but leaving the documents at home is not tolerated!
遅刻するのはまだしも、資料を家に置いてくるのはマズいよ！