Many people (me included) don't trust Google to stay with any business besides advertising. There's been too many times that they have ended services with not much time to get off.
I can understand being upset about their consumer products but it doesn’t really apply here.
The more services you put under one banner, the more the stink of one disaster is going to linger, and hinder adoption of the successes.
To me, a far simpler proposition would be a new brand & share issuance for each new sub-company (eg. Waymo), with existing Alphabet shareholders getting pro-rata shares in the new company.