I’ll throw in some ideas, maybe it’s useful for you. Just the basic ideas which can have any number of final results based on the setup.
You can use a single skylight, with a single sun, both as dynamic lights and no shadow casting. First add the skylight, tweak it to create ambient light, not too bright, usually done with blue-ish color, but tweak to your liking, it is stylized after all. When you have that add the sun, also without shadow casting and tweak it to compliment the skylight color and brightness. With this method you get same lighting and shading on everything and still get a sense of direction on the lighting, and bonus, no light maps.
Another method doesn’t even use lighting, but totally different look. You set up your materials with emissive using basically an inverted fresnel shading. Meaning in stead of shading light to dark from the outer edge, it shades dark to light. Set your color map as emissive through the inverted fresnel. This can be set up in a way where nothing ever goes black but still retain some simple shading. It’ll take a bit more than just inverting the fresnel, but it’s a fairly simple setup and can easily be tweaked. I mean, you can get creative here, what I mention is the basic idea. I have experimented with this in different forms before, it can be pretty cool, and useful. This will have no directionality to your shading, it’s always camera facing, but you can get a nice effect with it, also still maintain normal map details… etc. and of course again, no light maps to deal with.
You can also combine the methods. Use emissive as a base shader, but use a sun without shadow casting as a light source for some directional shading. So, no skylight, meaning cheaper lighting. You can even use shadows and have interiors be darker in general, and on top of that make use of the eye adaptation post process to handle interior brighten… etc… I mean, there are a few things you can do here to get simple but good lighting and shading without having it look like an old game, you know…