Interestingly enough though, "Luca" restaurant opened in 2001/2002 just off Av Liberdade if I remember correctly and has made a killing ever since, with lunch and dinner fully booked out even without the parking space.
Nightclub will probably be tougher to find a good location as there are still a lot of residential areas on Av Liberdade, and people want to drive to a venue and then walk from one bar/club to the next. However the location could probably be a good choice for a restaurant or bar (assuming you envision something different than the traditional "tasca" or "barzinho" of which there are dozens all over the place). People can always get the metro to your location and have a nice little walk down to the Rossio (to go to the theatre after an early meal) or up to the Bairro Alto.
So while I agree that traditionally Alcantara, Av. 24 Julho and Expo area are generally the more logical locations, the fact that there are very few medium-upscale options on Av. Liberdade could be a boon. In the Alcantara area specifically there are not only dozens of trendy bars and restaurants available but also most of them are established venues which will be heavy competition for a new opening.
