You have to realize that a modern, smooth, interface and workflow is the result of significant resources -- both hardware resources, and development resources. Most products that feel good have user interaction designers, graphical designers, and software testers involved in addition to software engineers. If your previously software was developed by a software engineer without those additional resources, it's reasonable to see why it couldn't easily be updated.
Secondly, because of the number of people involved, the cost will also go up. Without knowing your budget, it's hard to give any kind of recommendation. I know top-notch contracting houses with award-winning artists, very senior engineers, and dedicated project managers on staff. They will bill you $250 per hour per person, and the application you're suggesting is probably around 600 person-hours assuming a stereo vision library can be found for the stereo analysis part. You'd get a great application! And it would only cost you $150,000! If you'd like a reference, I'd be happy to forward it if you private message me; no relation with them except as a satisfied customer.