I spoke about this recently but it really is our most discussed topic of conversation at library sessions. Somehow on the internet it always turns into a big topic of debate but it's actually extemely simple.
So, here is the benefit of being a babywearing consultant for over 12 years:
Your baby CAN wear sleepsuits in a sling or carrier. Just make sure little toes aren't being squished by giving the fabric a bit of a tug in the foot bit of the sleepsuit.