Yes. For one, you can build the wall specifically to hold the suspended shelf. And you don't have to demo anything and start all over.
Before I make any suggestions, I want you to know I'm not an engineer. I build furniture as a hobby and have learned a lot about wood and strong joints but am by no means any kind of expert. And while I would build it this way, I can't guarantee this will be rock solid. But I would be surprised if it failed.
I drew up some plans the way I would do this and created some cut-away views for clarity. BTW, this would be a pretty permanent installation.
I went with a mortise and tenon joint to connect the horizontal members to the vertical ones. I'm using all 4x4s and would use Douglas fir over construction grade pine. I'd prefer oak lumber but I'd hate hiding it in the wall. Still, the more I think about it, the more I would tend towards the oak. Then I'd figure some way to leave the back of the wall open as an accent feature, such as a wall behind a bar.
The wood you use would have to be seasoned. If you went with oak, that would mean leaving it in your basement for a couple of weeks to acclimate to the humidity.
The mortise and tenon joints wouldn't be all that difficult, even if you've never done it before. There are only three. You could do it all with hand tools but would need a good saw and some decent chisels. You could speed up the process of making the mortise with a drill and a forstner bit. If you don't own any forstner bits, I'd buy one the same diameter as the dowels you intend to use (3/4" in the images).
The reason I show wood dowels instead of screws or bolts is because wood shrinks and swells and metal doesn't (at least not like wood). As wood swells around a bolt or screw, it gets crushed. When the wood shrinks, it creates a looser fit around the bolt or screw.
All the joints have to be very tight and everything would be glued. Glue loses its effectiveness if the joint is loose so take your time and make all the joints snug. Start with the mortise and fit the tenon to match. This is a decent video showing how it could be done just with chisels and a backsaw: http://www.youtube.com/watch?v=LPBkO2chZxk
I added the dowels for additional strength. All that would require is drilling holes and inserting glued-up dowels, a simple step that would add a lot of strength.
The plywood can be attached with finish nails or clamped with construction adhesive if you don't want to see or fix nail holes. If you're good with a circular saw and have a straight edge, you can cut a 45 degree bevel all around the edges to create the appearance of the shelf being one solid piece. Apply glue to all the edges and finish it off with a wood putty matching the wood tone.
On the back side, I added backer blocks on either side of the horizontal members so you have something to nail the planking to. If you decided to put a bar on the other side, this wall could be used to hold shelves for glasses and such. The backer blocks and additional studs should be the same wood as the 4x4s to give it that finished look. You may be able to find some reclaimed lumber for the wall framing.
If I were to take on this project, that's how I'd do it and I think not only would it hold, but it would look pretty cool. And I'd build the bar too.
If this seems overwhelming or too time consuming, just think of all the enjoyment you'd get out of it, not to mention bragging rights.