Looking at some of the proposals, it seems that there many which should be merged, on the basis that the combined interested user base will be large enough to support the site.
Good examples are all of the various proposals on individual games (such as Go and Chess). Do those who commit to these proposals really think there should be a SE site devoted entirely to such a narrow scope? Shouldn't these sites be proposed with a wide audience in mind, with the possibility of splitting later, if things get too cumbersome? I just can't see a SE dedicated solely to Chess ever growing to a significant size, unless all the professional Chess players in the world routinely contributed. What about questions that ask "Can chess strategy contribute to my methods in X?" where X is some other game. That would be off topic on a Chess site, but much more welcome on a site for all such styles of game. Yet chess experts might certainly be needed for their insight on the answer.
The same can be said about a few others that may struggle in the beginning. I am a Bird enthusiast and committed to the Birds proposal, but it occurs to me that it should probably be merged with Nature and Wildlife, along with any other proposal that is so narrow yet related.
The various engine, motorcycle, and automobile proposals should all band together and work on a site that has a large audience. One user suggested that motorcycle enthusiasts have a mentality of being separate from other motor vehicles. That is probably very true on the road, but I am willing to bet that motorcycle and automobile mechanics and enthusiasts would share a lot of common ground when it comes to Q&A about their respective machines. At the very worst, just ignore the tags of the things you don't enjoy once the site is live.
Of course, I never would have thought there was a large enough audience for TeX and LaTeX, or for GIS. However those proposals don't seem to have a very logical umbrella category under which to place them.
So, fellow StackExchange users, do you agree that proposals should start out with a Breadth-First mentality, or continue with the Depth-First approach that seems to leave many proposals floundering at the bottom?