I would like to support the request for ALL exercises to have the animations. I don’t like using the “video instructions” option. What if I have no internet and I want to do a workout but I don’t know the movements?
I do agree it would make the app heavier to download but I believe that the benefits of all exercises having animations are far greater for all users than that minor inconvenience with the slower download and a little bit more storage used. 
Maybe you could consider implementing the animations for all exercises and giving the user the option to not download them? 

I would like to suggest integration with Garmin watches. Those specifically sports watches and they do have a Strength training option which incredibly useful in the gym.