I wore my son everywhere! I must have owned ten slings, and made most of them.
My tube type made out of stretch material looked similar to the knitted one shown for sale. My advice if you do go ahead would be make it tighter then you think it should be. My tube one had to be resewed tighter and tighter every so many months as baby grew. So I wonder how long these types of slings last if knitted.
It would be perfect for a newborn to about 4 months with the baby in cradle hold. It can be done, but I'm afraid its usability wont last very long.
One more caution. The ones being sold online are machine knitted. I have a machine knitter and my fabric made on it versus my hand knitting is much stronger. FWIW.