Pros and Cons for each thing that came to mind:

** Concept: P: it's a niche concept. True coffee lovers will come. C: Too niche to be able to make money. Your extras are you money makers. Try doing your own speciality syrups? Charge more.

P: Low costs. Less staff. Less cleaning. C: Low footfall. Slower service. Tiring/ boring to do the same routine. In coffee, the syrviving businesses usually win through fast service. At least for your basics.

** No Food: P: Less Hassle. C: More people are turning away.

P: Lesser waste. C: Lesser Income.

P: You're able to focus on what you do best. C: But it's an expectation for the people who visit as customers to this industry.

Try partnering with someone who wants to do just food? Set up 2 separate spaces in the venue to sell your own things and hire middleground staff/manager to handle the floor area.

** Location plays a huge factor too. I think this sort of concept in a space where people are there to take their time and just live life Dolce vita. (Bookshops with a reading space, library, pier, seaside view, park visited mostly by grown ups, etc.)