RCR is the proof that people will visit and spend time in restaurants if they are enticing enough, be that via their gimmick or quality of offer; RCR clearly being the former.
I understand the reason for perhaps not locating a restaurant on Towers Street, since it is one of the quietest areas of the park around lunchtime. That said though, with CBeebies Land being ever popular and the addition of what appears to be a semi-permanent stage, that area is now likely to be busier than perhaps it would have been a few years ago. Would a full refurb of Towers St Restaurant be popular, if it offered similar enticement as RCR? Perhaps a Sir Algenon restaurant, which perfectly overlooks the Towers and with the addition of a few characters could work. Darwin has made a spectacular comeback, so him and Sir Alg walking around the restaurant might be a nice USP, with no need for an IP licence.
You could sell it to people with the characters as they wander in or offer a bolt-on to ticket purchases perhaps. Later opening hours also offers the opportunity to cover both lunch and dinner time services.