Said with love and kindness......you both are assuming certain things that are wrong. This is to be expected, most people these days have no idea what to expect during labour apart from what they have seen on TV. And that at least is more than women of my age had as we didnt experience our mothers or aunts or sisters birthing at home, and One Born Every Minute would very much NOT have been on TV in the 80's!!
I have had 6 births and I wore something with all of them except one where for some reason I couldnt bear anything touching me at all. So your DH is wrong on that one. The midwives frankly couldnt have cared less what I was wearing as long as the business end was available as and when needed.
That said......taking knickers on and off when full term is a big enough pain in the arse (har har) when not in labour, doing it when labouring and you may not be able to move particularly well (due to epidural, pain, chosen position etc) is far worse. Do it once and chances are you wont want to try and put them back on again, then off again etc. You are coming at this from the POV of a woman who isnt full term and isnt in labour, when the moment comes you will realise that there are more important things taking up your thoughts than whether you have your knickers on.
If there is one thing I can suggest to any couple planning their first labour....dont bother. All the birth plans in the world wont make this controllable. You will not bein charge, your body and your baby will be. I would say that coming to peace with what your body and baby want and need in the moment will help you go with the flow better than trying to plan everything in advance and then being angry or guilty or lost when the plan doesnt happen.
Its scary and human nature is to try and remove the fear by trying to control the outcome, but you cant.
One way or another, your baby will make its way into the world, knickers, sport bra or nightie notwithstanding. You'll do fine xx