High five - I wear Cafe Au Lait in Nubian Skin too (although I only have a bralette) lol!
I think it's not just a matter of the depth of the shades being unavailable (although I do acknowledge & therefore struggle with it too) but it's also a matter of the undertones - there's a lot of 'yellow' nude underwear on sale here (given the local population) but it still looks like I'm wearing Day-glo undies if I try it because it's all a very specific, cool toned yellow lol.
To answer your question though, I assume pettipants are similar to the bloomers I wore when I was younger (although those closed at the ends with frilly hems instead of an A-line shape) - honestly most clothes wouldn't lie so well on top of them because they were essentially adding extra fabric (which means your skirt could still get caught between your legs lol). So I think they could work for looser bottoms, but I'd check the fabric to ensure they don't cause any bunching or static.
Personally, I like Uniqlo's body shorts in mauve or as my winter slipshorts (they also have one specific shade of mid brown bra that works for me lol) & Intimissimi's supima cotton bike shorts for the summer. They've released a cotton non underwired padded triangle bra that intrigues me, but am not yet brave enough to actually try whether their 'mid brown' colour bra will actually be nude on me (for fear of disappointment) lol
(PS: If anyone else is interested in minimising chafing/ chub rub without having to wear full slipshorts, I've heard 'bandalettes' do a good job of protecting the thigh area without slipping - so you can wear them with your usual underwear).
