I've said this before, I wish you were closer so I could get private coaching.
However, IMO I would do this. You may not be able to catch every little detail, but you could certainly help alot.
First I would do a coaching and form DVD. A good shooter the shows your methods as an example with you doing the explaining.(Hopefully something Prettier to look at than just you.
Second you can do personal consults, as long as you have video from multiple angles otherwise its hard to really see. However you have a good knack for being able to diagnose shooting problems over the phone. However this requires the shooter to be honest about whats really going on in their shot process.
Should you charge for it. Absolutely. Its alot of your time. Which is worth charging for. I don't work for free neither should you.
What do you charge for Private coaching now???? How in depth would you plan on getting with this phone/internet coaching??? What level of Shooter are you planning on taking on???? Is this form coaching or mental coaching????