Your assuming everyone has high speed. I think you also assume everyone has a smartphone.
AOL still has 3-4 million dial-up customers.
The small ISP i still own but walked away from last year still has a couple hundred dial-up customers.
The town i live in, is surrounded by a half dozen towns that do not have high speed available. I lived in one of them last year and that one did not even have cell phone service or cable tv.
And personally, if someone started attaching videos to emails being sent to me without me specifically requesting them, i would report it as spam.
Sorry. Just my opinion. I was a internet provider for over 10 years. I had to deal with customer complaints about spam, large attachments they could not download, photos, ect. Email and the abuse of it for uses that email was not designed and intended for is a touchy subject for me. Not everyone lives in a big city where high speed internet and iphones are as common as oxygen.
Anyhow. Food for thought. Something to consider before actually doing it.