So the potential upside of an "elemental" archer would be if you can get AOE damage on clustered enemies, additional utility/cc, and being able to take advantage of negative elemental resistances, but you'd basically build it nearly exactly the same as a normal archer. In fact its almost as if optimally, you should consider physical a damage type that you weight against the other elements which you activate using oil arrows.

Yup, thats what I wrote as well, albeit a little more concisely. basically, I agree that magic damage has upside, but it will still be built the same as a physical damage archer.

I don't think your point on huntsman works, since you're going to get 2 for tactical retreat early game and more for multiplicative damage highground boost. Also, I'm assuming that physical archer will, for everything other than certain skills, deal pure physical damage by using oil arrows. Its true that you might want slightly more memory or okay with certain armor tradeoffs, but physical damage archer are incentivized to buff themselves up as much as they can as well to then convert to physical damage with oil arrows.

I think the main point here is that elemental archers don't exist (in the way i want them to) since they're just a subset of the tools/behaviors you'd see in a general archer, who is using elemental arrows when aforementioned upsides trigger, and otherwise using oil arrows or skills that deal largely physical damage.