Why nobody thought of such a concept? Because it doesn't work mainly. Or at least there are problems:
People don't go to kopitiams to hang out. Stall owners don't encourage people to go to kopitiams to hang out, unless it's downtime (after lunch hour). As you know, kopitiams are either really empty or full. If it's really full, you got no chance. The kopitiam stall owners knows that anything that takes up space, or makes the customer stay more than 20 minutes at a place is not an option. And anything that they have to pay for - even if it's $10 - is not an option either.
I am an engineer. When I go out for lunch with my colleagues I want to be discussing problems, cutting deals or bitching about my boss. I don't want to be listening to live music.
During downtime for the kopitiam is when you have more choice. But during downtime, people will want to go to kopitiam to talk cock with others, or to watch TV. You might have to compete with all that. And I don't think that you'll get any money from the stall owners, because downtime is not a profitable time for them. Maybe a better business model is for you to be busking in a kopitiam, and hopefully during that hour you can raise $50. And you'll have to see whether the authorities or the neighbours of kopitiams allow it or not.
And if you want to be busking in a kopitiam, why not busk in a neighbourhood town center instead? And why not establish a tradition where you busk at a pasar malam? Or you play your music at getai festivals?
One of the biggest impediments to live music in Singapore is sky high property prices. Second biggest impediment to live music in Singapore is sky high alcohol tax. Both these things mean that opening an entertainment spot in Singapore is very expensive, and therefore there are restrictions.
As for freedom of speech as an entertainer in Singapore, forget it:
http://othersounds.sg/news/local/gr...-out-of-club-after-voicing-political-beliefs/
I know that I probably shouldn't be a wet blanket, but it's also important to not try things out that will probably not work.