I've made a few carriers. If you have the time and the skill there are definite benefits to making your own. There is a free pattern for a structured soft carrier like an ergo in the DIY forums of the babywearer, so I think that would be a good place to start.
I also like to be able to see and feel a carrier before I try and make a "copy" of one. I've actually not been happy with my beco, or my babyhawk and the Mei Tais that I've made have been much better suited to me.
Just be sure to use safe materials, and safe stitching.