yes to 1 and 3. 2 depends on what are my other choices. Visibility is important for me. Since white shuttle travels very fast, line visibility on the floor is important to judge shuttle in/out, especially since my eyesight is not 20/20. I have been troubled by light colored lines on hardwood floor in HS gym that confused me if it's in or out. I'd argue visibility of lines are more important to badminton than basketball. Judging in/out is essential for winning points in badminton, but not in basketball. At the very least, have 2 courts be standard size and distinct lines so serious games can be played on these 2 courts.
Line visibility is also very important. When I judge a long shuttle I always only look at the shuttle to be ready to hit at any time. I judge where the line is by the low corner of my eye so I don't really focus on the line. It's like 15% sight, 85% estimation. So if you elongate the court and also have a lot of lines on it, I would never play where you stay lol.
court size i have played on courts with allsorts of lines on court for fifferent sports, they all tend to be marked out in different colours though, so while not ideal, you do get confused at 1st once you sort out your correct serving/returning position tend not to notice other lines as you get into the match,
I couldn’t convince the manager that 4 inches in length really matters in badminton. Hopefully, this will be corrected in the future when they have chance redoing the layout.
You can let the manager do whatever he does, at least, he can help you get most of the lines painted. Then, you can always get some tape to "correct" the ones you would like to fix, if you do care.