I've been in a similar situation with my basement. Cracking thin layer of concrete straight on the soil. I removed all the concrete, dug out the soil to fit proper, insulated floor and gain some height and poured the concrete. Basement only had small windows but, since I was doing the whole house, I turned one of them into external door with stairs. A lot of work but best decision ever.

To answer the question. The main issue with lack of external door is getting rid of old concrete and soil underneath and it looks like you have to do it because of limited height. When this is done pouring concrete is a breeze as it gets mixed outside and pumped inside with a pipe (through a window). It's one of those jobs that are better/cheaper done by a pro instead of diying. Putting pavers after removing old concrete would be pointless imo.