Blossom and IPFS are Web3, for most definitions of the term. Nostr and Lightning are too, when people run their own nodes.

Possible to do this: yes

Ease to build: easy - cameras can record local video, apps already exist to upload into #IPFS, nostr link can then be shared as http://localhost:8080/IPFS/ (some CID hash). And nostriches with an IPFS app could just view it.

Likelihood of mass adoption: pretty low

Unfortunately. 

Workflow too complex, video stream too slow