I have to agree with Toast. Actually there are not only free modelling tools, there are also free programming IDEs with very good debugging and highlighting capabilities. And there are tons of free help documentations for it.

Actually a game engine is about, guess what: a game engine. This is the part that renders the world, that does the culling, collision detection, scene management, loading and playing sound, memory management, streaming, object management, input management, lighting and so on. The only needed but very important tool for such a technology is a good world editor with decent import capabilities of models, textures, strings, fonts, gui-elements, sounds and whatever I forgot to mention.

Actually I am a fan of having as much tools as possible in a software package. Because of that I like to work with complete modelling, rendering and animation packages like Lightwave or Modo. But I just experience in this moment that Lightwave gets separated more and more. Earlier it was Modeler and Layout as 2 separated tools (connected by a tool called Hub). Now it is Layout (for animation and rendering), Modeler (for modelling), Hub (for data exchange) and Core (as a new generation modeller and renderer). Modo on the other side has everything aggregated into one application and it just feels better integrated.

So from my own experience it would make more sense to aggregate tools.

I also agree with Toast about the niche idea.

By the way: I would not classify my post as a rant. I hope I just mentioned some constructive points and ideas. This in mind I find the name of the forum section not a good choice. Maybe mentioning this is somewhat of a rant though