DAA,
I'd suspect that one of the readily available ballistic type reticle scopes can be tweaked via mag setting to account for a target size of your choosing. A quick test at given yardage with a yard stick and a log for the info could help alot if trying already available reticles.
Finding one tailored to your needs poses a dilemma. Devising a custom reticle based to your specific rig & load combo would be the cat's meow! I pondered idea of using a FFP reticle so as not to be at the mercy of a specific magnification setting while ranging a target via reticle subtension. But the size of target remains a variable in the equation. And price point of front focal plane glass is somewhat of a hindrance as well...
You are spot on, hitting anything at over 300yds really becomes a challenge. Getting the job done beyond that proves to be an interesting & enjoyable challenge to tackle. There are more than a few guys here that find this kind of stuff fascinating.
As for the videos...
Heck, I didn't even know they were on the market until this dialog exchange w/you. Admittedly, I'm a hunting video wh**re and pretty sure I'll enjoy the heck out of them!
Regards,
Fred