My answer is similar to that of Pete Clark's.
Ethically, as long as what you write is sincere, you can arrange your results in whatever way you want in papers, and you can publish them in journals or not as you please. If you look at the way that many strong mathematicians write papers, some of them simply break every rule that you can imagine as to what "should count" as a paper. They can get away with it because they are trying to do something hard. For instance, Perelman's papers are extremely telegraphic and break a lot of rules. As it happens, they aren't published in journals, but no one cares, other than that I'm sure that many journals would love to have published these papers.
Unfortunately, if you need a job, the letter of publishing ethics is more important than the spirit, unless you game the system to some blatant extreme. It is just the mechanics of job searches and not the fault of any one search committee. You get almost no penalty for publishing small results; on the contrary it is risky not to expand a good result into several papers. In any case, many published results are routine extensions of known mathematics, dressed up by including every little detail of "the proof". Up to a point, even that is ethically fine. Unfortunately, it really is true in both hiring and promotion that quality is controversial, while quantity is an objective standard. (Even though quantity is also a highly distorted standard that is not measured in a consistent way.)
Mathematics is rigorous (ideally), but mathematics journals and the mathematics profession are not. I don't think that it works to impose axioms on the latter two. It's not that I don't care or that I believe that there are no standards, but I would rather see common sense than strict conventions.