Chris, the closest I get to alternative process is azo, which isn't like what you are proposing. It is possible for me to get a film which can work with both azo and silver enlarging paper, but grade 2 azo is not grade 2 silver. That having been said, there is always some talk about the staining properties of certain pyro developers which are able to build highlight density in the U.V. range, so that the extended range does not show up on silver papers. Pyrocat does build "extra" stain in the highlights, which doesn't show up in a "normal" silver print because of its actinic properties. PMK does a similar thing, but introduces a general stain which reduces contrast in some values of the print. I haven't used WD2D+, so I don't have any tests on this one to compare.
So yes, it is possible to have a dual purpose negative which works for both silver and other types of alternative process printing, but you would need to do some testing in order to match your paper's scale against that of the film. I think what you may find is that a variable contrast silver paper can be made to work with a film designed for another process. As far as a perfectly tailored film which can do platinum, azo, silver, cyanotype and Van Dyke, I don't think so. There are too many variables in paper contrast, especially in alternative printing, to have one negative work reliably for both.
I have used Efke 25 a fair amount in the last 2 years, and I would have to say that it would be as good as any for what you are asking, and perhaps better than most. It does build density and contrast like there's no tomorrow, but you could probably use Efke 100 with greater ease, as it isn't so persnickety with respect to development times. The 100 is much easier to develop due to its long tonal scale and longer working times. Just my opinion. tim