Yes a herd of elephants getting stuck on a narrow path is somewhat acceptable but in the video the bouncing was way too awful.  The reason why I would give this new "solid" propriety to only melee elephants amongst all land units, is that it's one of the costliest units. And "solids" having inelastic strong pushs, it will always make a large group of such "solids" always a bit tricky. But it doesn't mean that it should look as sh!t as in your video neither.  I found a few bugs, improved some of the physics, and made couple tweaks that try to address that. Ideally we can still have "solids" do the minimum of overlapping. Tell me if you manage to test and still reproduce the weird bouncing!

I made a post asking for references. What do you mean by the original? I used several references. I created it from many interpretations of Helios. I used one I saw as a base. It can be easily changed.

Chosen Athenian sounds a bit strange tho, maybe “Chosen of Athena”? Same meaning, but reorganized name.

A new release is planned soon, but till then I hope this holds y'all over: https://www.moddb.com/mods/hyrule-conquest-revival/news/lots-of-new-stuff-coming-soon

I would still argue that athens unit tree should still include slinger, but they're only recruitable from the civic center, are cheaper than most other slingers, but are far weaker because of their cheapness (less range, slower movement, lower damage, or other choices). In essence psiloi. My other suggestion would be if slinger psiloi do become implemented, they should not be able to level up, though I feel this would be more of a gameplay balance sort of choice rather than an actual historical one.