Should a search be abandoned if it doesn't fit into a "keyword wedge"?

[ron-for-your-life]

By keyword wedge I mean the right fit between too much seoc and not enough of seot and pbr. I suppose what i'm asking is if a market hasn't been created yet, say, for example, "sports bicycles for oversized persons" (didn't research this one yet, you all can if you want too!), should it be tossed. Or is there a way to develop a new niche cost-effectively, and quickly.?
I've typed-in keywords, only to find them too competitive, then added an extra keyword with some promise to it only to find it under-active, yet it "feels" right. (I know you've for-warned us all about feelings getting in the way). If it's outside the wedge, is it a time-waster?

[DeanRichards]

...is there a way to develop a new niche cost-effectively, and quickly.?

In a word, no.

It is possible to develop new markets and it is done all the time. But it certainly isn't easy or quick, and frankly, if you're not already an expert in how to do it, you're going to be wasting your time.