Your statement about particles, i.e. matter vs. your view of what dark matter is "fairly likely to be" brings up a question. I have been considering dark matter to be a product of nucleosynthesis that does not emit electromagnetic radiation but does have mass. As such dark matter would be a relic of the period of matter formation that never completed the process of becoming fundamental particles. They wouldn't become incorporated in objects composed of matter but would gather in and around matter. The density of dark matter would be higher around galactic structure and lower in the expanding reaches of space between galaxies.
Hmm, I am not clear on what you are suggesting. Nucleosynthesis doesn't involve the production of fundamental particles. Nucleosynthesis refers to the production of atomic nuclei (i.e. the nuclei chemical elements) from protons and neutrons, which even themselves are not fundamental particles (being composed of quarks, which are). There are some neutrinos and electrons and such created during these processes but I don't think that was what you meant.
If you are suggesting the dark matter particles did not take part in nucleosynthesis then yes you would be in agreement with most dark matter models, being weakly interacting they would hardly influence nucleosynthesis at all. There is some evidence for dark matter that comes from the relic abundances of the elements from primordial nucleosynthesis, but to be honest I'm not sure how it works exactly. It might be simply that based on the gravitational evidence there is more matter than can be accounted for by the products of nucleosynthesis in the conventional models, but there may be more to it. Here is a passage from a review paper I read, but unfortunately it doesn't really give reasons:
"When the universe was a few hundred seconds old, at a temperature of ten billion
degrees, deuterium became stable: p + n → D + γ. Once deuterium forms, helium
and lithium form as well. The formation of heavier elements such as C, N, and
O must wait a billion years until stars form, with densities high enough for triple
interactions of three helium atoms into a single carbon atom. The predictions
from the Big Bang are 25% Helium-4, 10−5 deuterium, and 10−10 Li-7 abundance
by mass. These predictions exactly match the data as long as atoms are only 4%
of the total constituents of the universe."
Freese, Review of observational evidence for dark matter, astro-ph > arXiv:0812.4005v1
The stuff you said about how dark matter is distributed, i.e. "They wouldn't become incorporated in objects composed of matter but would gather in and around matter. The density of dark matter would be higher around galactic structure and lower in the expanding reaches of space between galaxies.", is pretty much the current understanding of the dark matter distribution, except that the 'causality' is thought to be the other way around. Since there seems to be so much more dark matter than regular matter, galaxies and galaxy clusters (i.e. ordinary matter) are believed to have formed where they did BECAUSE of the high dark matter density there, i.e. the dark matter is highly responsible for the many of the large scale structures observed in the universe.
So possibly what you are suggesting is more or less in line with the conventional dark matter thinking. If were talking more about the very INITIAL 'production' of the actual fundamental particles, i.e. perhaps during some supersymmetry breaking process (quite a few dark matter models involve supersymmetry) or electroweak symmetry breaking or something then that would be a different discussion.
edit: Actually just one more comment on this:
Thanks AN, but matter consists of more than charged particles. I mentioned both matter formation and nucleosynthesis. There are hadrons and leptons that formed before the charged particles but it all happened in the first moments.
Hadrons fall into two categories, baryons (things made of 3 quarks, i.e. protons, neutrons and some more unusual particles) and mesons (made of a quark and an antiquark, things like pions and kaons, all of which are pretty unusual), both of which can be charged (clearly protons are charged) because quarks are charged. Leptons are simpler, and they are all fundamental particles. There are only 12 of them, i.e. electron, muon, tauon, a neutrino for each of these, then an antiparticle for all 6. These are all charged too, except for the neutrinos. So I don't really know what you meant with this statement.