1.Nf3 c5?

How do you counter 1.Nf3 c5? Is it possible/advisable to go for a typical Reti setup, or should one abort the Reti-idea and transpose into something else?

After 1.Nf3 c5 2.c4 you have the Symmetrical English. I would definitely switch to a different opening. For me that would be 2.e4 and a KIA vs Sicilian because I am familiar with those lines.

I see, thanks! Are there any other responses where one should abort Reti and transpose into something else?

after 1.Nf3 c5 there is also 2.b3 going into a reverse English defense which can also transpose into Reti vs QGD lines where b3 is often played

1.Nf3 c5 2.b3 is a Nimzo-Larsen.