If it has more than 1 change table in then I generally wouldn't lock it. The only time I would lock it was if my toddler was in one of her bolting moods when trying to change the newborn or if you have an older child with SN who needs a change. I would be a bit 🙄 at a locked multiple change room with only 2 adults and a baby in but wouldn't say anything. My little one has horrid teething nappy rash and needs a quick change, she also absolutely hates been wet or dirty so would the screaming and thrashing about making waiting hard work.
Personally I think sticking a feeding chair/ cubicle in the baby change is grim (for both the mother and baby). Baby change rooms absolutely stink and are usually really busy so not even offering a quiet space a nosy baby needs.
You will realise in a few weeks baby change spaces are limited and in high demand. They are either put in the disabled/ all inclusive toilet or they have 1 baby change room with multiple change tables. I say this gently but I think you need to prepare your wife for when you are forced to use the disabled toilet as that's where the only baby change is and there is a disabled person waiting to use it and they lecture or huff and puff at you using the disabled toilet. It would be great if places had separate disabled and baby changes but most don't and there are some disabled people who are (rightly) very protective of those spaces. The recent adoption of most disabled toilets also now considered a toilet for everyone also seems to have added additional pressure to their protected space. Maybe I have been unlucky in my medium size shopping centre but every time I go there I and other mothers witj prama are confronted or huffed and puffed.
The only time it would take 2 to change a nappy is in the case of massive poo explosion that covers clothes or when you get to the wriggly, demon possession at nappy change phase when they fight you, wriggle, roll and struggle whilst screaming like a banshee.