My oldest used to carry his baby sister all the time, but in the Baby Bjorn (which I know some folks don't like) but I felt comfortable with that. My son , 10 at the time, spent many hours helping be another pair of arms. He carried her in a maya wrap at home as well, but I was always a little more concerned about that...I mean, even I've dropped an older babyfrom a sling once. So, when we were out and about, the park, market etc and he wanted to carry her, it was in the BB. He also like the packpack when she got older.
As for not using items to carry...I let the children carry babies. My oldest were 5 and 6 when the last baby was born, and they carried her to me all the time. My oldest was 10 and changed diapers until the baby got too wiggly (and too smelly for him) lol. When my oldest was not quite 5, my 3rd was born and he used to carry his brother to me if he heard him wake before I did. I remember a cousin of mine absolutely freaking out at a family gathering when my 5 yr old carried the baby to me for changing. But he was very careful-- he was born old.
It would depend on the child, you know? Just teach them how to do it safely.
I have some great pics of my kids babywearing. Front backs, wraps, backpacks. Sweeeeet. I also think having older kids around to hold babies is an absolutel godsend. You don't much need carriers or boppys etc., as there are always arms to hold the baby. I remember when my 3rd was 5. He was great at holding so I could pee or take a quick shower.