I think some of you seriously underestimate the spending power of leisure and LCC pax. The LCC sector is no longer so niche that it needs a totally separate terminal and its passenger profile varies greatly. Therefore, the facilities such as the retail outlets, and even lounges, are well patronised by passengers travelling on charter and low cost. MAN is still very skewed towards leisure, and increasingly LCC pax, but it's these types that spend in the terminal. They certainly do onboard too. MAN specifically is renowned amongst airlines to be a very lucrative base/station when it comes to onboard sales.... And not just drinks either.
So, when it comes to designing the actual terminal, don't totally disregard the needs of these pax. Often it can be the F and J class and frequent pax who glide through the airport spending little or nothing.
Where provision for the LCC's is required is gates closer to the runway, with infrastructure that supports slick turnarounds.